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* [PATCH net-next RFC 0/5] ipv6: sr: introduce seg6local End.BPF action
@ 2018-03-23 10:15 Mathieu Xhonneux
  2018-03-23 10:16 ` [PATCH net-next RFC 1/5] ipv6: sr: export function lookup_nexthop Mathieu Xhonneux
                   ` (5 more replies)
  0 siblings, 6 replies; 12+ messages in thread
From: Mathieu Xhonneux @ 2018-03-23 10:15 UTC (permalink / raw)
  To: netdev; +Cc: dlebrun

As of Linux 4.14, it is possible to define advanced local processing for
IPv6 packets with a Segment Routing Header through the seg6local LWT
infrastructure. This LWT implements the network programming principles
defined in the IETF “SRv6 Network Programming” draft.

The implemented operations are generic, and it would be very interesting to
be able to implement user-specific seg6local actions, without having to
modify the kernel directly. To do so, this patchset adds an End.BPF action
to seg6local, powered by some specific Segment Routing-related helpers,
which provide SR functionalities that can be applied on the packet. This
BPF hook would then allow to implement specific actions at native kernel
speed such as OAM features, advanced SR SDN policies, SRv6 actions like
Segment Routing Header (SRH) encapsulation depending on the content of
the packet, etc ... 

This patchset is divided in 5 patches, whose main features are :

- A new seg6local action End.BPF with the corresponding new BPF program
  type BPF_PROG_TYPE_LWT_SEG6LOCAL. Such attached BPF program can be
  passed to the LWT seg6local through netlink, the same way as the LWT
  BPF hook operates.
- 3 new BPF helpers for the seg6local BPF hook, allowing to edit/grow/
  shrink a SRH and apply on a packet some of the generic SRv6 actions.
- 1 new BPF helper for the LWT BPF IN hook, allowing to add a SRH through
  encapsulation (via IPv6 encapsulation or inlining if the packet contains
  already an IPv6 header).

As this patchset adds a new LWT BPF hook, I took into account the result of
the discussions when the LWT BPF infrastructure got merged. Hence, the
seg6local BPF hook doesn’t allow write access to skb->data directly, only
the SRH can be modified through specific helpers, which ensures that the
integrity of the packet is maintained.
More details are available in the related patches messages.

The performances of this BPF hook have been assessed with the BPF JIT
enabled on a Intel Xeon X3440 processors with 4 cores and 8 threads
clocked at 2.53 GHz. No throughput losses are noted with the seg6local
BPF hook when the BPF program does nothing (440kpps). Adding a 8-bytes
TLV (1 call each to bpf_lwt_seg6_adjust_srh and bpf_lwt_seg6_store_bytes)
drops the throughput to 410kpps, and inlining a SRH via
bpf_lwt_seg6_action drops the throughput to 420kpps.
All throughputs are stable.

Any comments on the patchset are welcome.

Thanks.


Mathieu Xhonneux (5):
  ipv6: sr: export function lookup_nexthop
  bpf: Add IPv6 Segment Routing helpers
  bpf: Split lwt inout verifier structures
  ipv6: sr: Add seg6local action End.BPF
  selftests/bpf: test for seg6local End.BPF action

 include/linux/bpf_types.h                         |   5 +-
 include/net/seg6.h                                |   3 +-
 include/net/seg6_local.h                          |  29 ++
 include/uapi/linux/bpf.h                          |  57 ++-
 include/uapi/linux/seg6_local.h                   |   3 +
 kernel/bpf/verifier.c                             |   1 +
 net/core/filter.c                                 | 385 ++++++++++++++++---
 net/ipv6/seg6_local.c                             | 170 ++++++++-
 tools/include/uapi/linux/bpf.h                    |  58 ++-
 tools/testing/selftests/bpf/Makefile              |   5 +-
 tools/testing/selftests/bpf/bpf_helpers.h         |  12 +
 tools/testing/selftests/bpf/test_lwt_seg6local.c  | 438 ++++++++++++++++++++++
 tools/testing/selftests/bpf/test_lwt_seg6local.sh | 140 +++++++
 13 files changed, 1235 insertions(+), 71 deletions(-)
 create mode 100644 include/net/seg6_local.h
 create mode 100644 tools/testing/selftests/bpf/test_lwt_seg6local.c
 create mode 100755 tools/testing/selftests/bpf/test_lwt_seg6local.sh

-- 
2.16.1

^ permalink raw reply	[flat|nested] 12+ messages in thread
* [PATCH net-next RFC 1/5] ipv6: sr: export function lookup_nexthop
  2018-03-23 10:15 [PATCH net-next RFC 0/5] ipv6: sr: introduce seg6local End.BPF action Mathieu Xhonneux
@ 2018-03-23 10:16 ` Mathieu Xhonneux
  2018-03-23 10:16 ` [PATCH next-next RFC 2/5] bpf: Add IPv6 Segment Routing helpers Mathieu Xhonneux
                   ` (4 subsequent siblings)
  5 siblings, 0 replies; 12+ messages in thread
From: Mathieu Xhonneux @ 2018-03-23 10:16 UTC (permalink / raw)
  To: netdev; +Cc: dlebrun

The function lookup_nexthop is essential to implement most of the seg6local
actions. As we want to provide a BPF helper allowing to apply some of these
actions on the packet being processed, the helper should be able to call
this function, hence the need to make it public.

Moreover, if one argument is incorrect or if the next hop can not be found,
an error should be returned by the BPF helper so the BPF program can adapt
its processing of the packet (return an error, properly force the drop,
...). This patch hence makes this function return dst->error to indicate a
possible error.

Signed-off-by: Mathieu Xhonneux <m.xhonneux@gmail.com>
Acked-by: David Lebrun <dlebrun@google.com>
---
 include/net/seg6.h       |  3 ++-
 include/net/seg6_local.h | 24 ++++++++++++++++++++++++
 net/ipv6/seg6_local.c    | 20 +++++++++++---------
 3 files changed, 37 insertions(+), 10 deletions(-)
 create mode 100644 include/net/seg6_local.h

diff --git a/include/net/seg6.h b/include/net/seg6.h
index 099bad59dc90..f450bc37d196 100644
--- a/include/net/seg6.h
+++ b/include/net/seg6.h
@@ -63,5 +63,6 @@ extern bool seg6_validate_srh(struct ipv6_sr_hdr *srh, int len);
 extern int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh,
 			     int proto);
 extern int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh);
-
+extern int seg6_lookup_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
+			       u32 tbl_id);
 #endif
diff --git a/include/net/seg6_local.h b/include/net/seg6_local.h
new file mode 100644
index 000000000000..57498b23085d
--- /dev/null
+++ b/include/net/seg6_local.h
@@ -0,0 +1,24 @@
+/*
+ *  SR-IPv6 implementation
+ *
+ *  Authors:
+ *  David Lebrun <david.lebrun@uclouvain.be>
+ *  eBPF support: Mathieu Xhonneux <m.xhonneux@gmail.com>
+ *
+ *
+ *  This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ */
+
+#ifndef _NET_SEG6_LOCAL_H
+#define _NET_SEG6_LOCAL_H
+
+#include <linux/net.h>
+#include <linux/ipv6.h>
+
+extern int seg6_lookup_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
+			       u32 tbl_id);
+
+#endif
diff --git a/net/ipv6/seg6_local.c b/net/ipv6/seg6_local.c
index 45722327375a..e9b23fb924ad 100644
--- a/net/ipv6/seg6_local.c
+++ b/net/ipv6/seg6_local.c
@@ -30,6 +30,7 @@
 #ifdef CONFIG_IPV6_SEG6_HMAC
 #include <net/seg6_hmac.h>
 #endif
+#include <net/seg6_local.h>
 #include <linux/etherdevice.h>
 
 struct seg6_local_lwt;
@@ -140,8 +141,8 @@ static void advance_nextseg(struct ipv6_sr_hdr *srh, struct in6_addr *daddr)
 	*daddr = *addr;
 }
 
-static void lookup_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
-			   u32 tbl_id)
+int seg6_lookup_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
+			u32 tbl_id)
 {
 	struct net *net = dev_net(skb->dev);
 	struct ipv6hdr *hdr = ipv6_hdr(skb);
@@ -187,6 +188,7 @@ static void lookup_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
 
 	skb_dst_drop(skb);
 	skb_dst_set(skb, dst);
+	return dst->error;
 }
 
 /* regular endpoint function */
@@ -200,7 +202,7 @@ static int input_action_end(struct sk_buff *skb, struct seg6_local_lwt *slwt)
 
 	advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
 
-	lookup_nexthop(skb, NULL, 0);
+	seg6_lookup_nexthop(skb, NULL, 0);
 
 	return dst_input(skb);
 
@@ -220,7 +222,7 @@ static int input_action_end_x(struct sk_buff *skb, struct seg6_local_lwt *slwt)
 
 	advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
 
-	lookup_nexthop(skb, &slwt->nh6, 0);
+	seg6_lookup_nexthop(skb, &slwt->nh6, 0);
 
 	return dst_input(skb);
 
@@ -239,7 +241,7 @@ static int input_action_end_t(struct sk_buff *skb, struct seg6_local_lwt *slwt)
 
 	advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
 
-	lookup_nexthop(skb, NULL, slwt->table);
+	seg6_lookup_nexthop(skb, NULL, slwt->table);
 
 	return dst_input(skb);
 
@@ -331,7 +333,7 @@ static int input_action_end_dx6(struct sk_buff *skb,
 	if (!ipv6_addr_any(&slwt->nh6))
 		nhaddr = &slwt->nh6;
 
-	lookup_nexthop(skb, nhaddr, 0);
+	seg6_lookup_nexthop(skb, nhaddr, 0);
 
 	return dst_input(skb);
 drop:
@@ -380,7 +382,7 @@ static int input_action_end_dt6(struct sk_buff *skb,
 	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
 		goto drop;
 
-	lookup_nexthop(skb, NULL, slwt->table);
+	seg6_lookup_nexthop(skb, NULL, slwt->table);
 
 	return dst_input(skb);
 
@@ -406,7 +408,7 @@ static int input_action_end_b6(struct sk_buff *skb, struct seg6_local_lwt *slwt)
 	ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
 	skb_set_transport_header(skb, sizeof(struct ipv6hdr));
 
-	lookup_nexthop(skb, NULL, 0);
+	seg6_lookup_nexthop(skb, NULL, 0);
 
 	return dst_input(skb);
 
@@ -438,7 +440,7 @@ static int input_action_end_b6_encap(struct sk_buff *skb,
 	ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
 	skb_set_transport_header(skb, sizeof(struct ipv6hdr));
 
-	lookup_nexthop(skb, NULL, 0);
+	seg6_lookup_nexthop(skb, NULL, 0);
 
 	return dst_input(skb);
 
-- 
2.16.1

^ permalink raw reply related	[flat|nested] 12+ messages in thread
* [PATCH next-next RFC 2/5] bpf: Add IPv6 Segment Routing helpers
  2018-03-23 10:15 [PATCH net-next RFC 0/5] ipv6: sr: introduce seg6local End.BPF action Mathieu Xhonneux
  2018-03-23 10:16 ` [PATCH net-next RFC 1/5] ipv6: sr: export function lookup_nexthop Mathieu Xhonneux
@ 2018-03-23 10:16 ` Mathieu Xhonneux
  2018-03-23 10:16 ` [PATCH net-next RFC 3/5] bpf: Split lwt inout verifier structures Mathieu Xhonneux
                   ` (3 subsequent siblings)
  5 siblings, 0 replies; 12+ messages in thread
From: Mathieu Xhonneux @ 2018-03-23 10:16 UTC (permalink / raw)
  To: netdev; +Cc: dlebrun

The BPF seg6local hook should be powerful enough to enable users to
implement most of the use-cases one could think of. After some thinking,
we figured out that the following actions should be possible on a SRv6
packet, requiring 3 specific helpers :
    - bpf_lwt_seg6_store_bytes: Modify non-sensitive fields of the SRH
    - bpf_lwt_seg6_adjust_srh: Allow to grow or shrink a SRH
                               (to add/delete TLVs)
    - bpf_lwt_seg6_action: Apply some SRv6 network programming actions
                           (specifically End.X, End.T, End.B6 and
                            End.B6.Encap)

The specifications of these helpers are provided in the patch (see
include/uapi/linux/bpf.h).

The non-sensitive fields of the SRH are the following : flags, tag and
TLVs. The other fields can not be modified, to maintain the SRH
integrity. Flags, tag and TLVs can easily be modified as their validity
can be checked afterwards via seg6_validate_srh. It is not allowed to
modify the segments directly. If one wants to add segments on the path,
he should stack a new SRH using the End.B6 action via
bpf_lwt_seg6_action.

Growing, shrinking or editing TLVs via the helpers will flag the SRH as
invalid, and it will have to be re-validated before re-entering the IPv6
layer. This flag is stored in the skb control block, along with the
current header length in bytes.

Storing the SRH len in bytes in the control block is mandatory when using
bpf_lwt_seg6_adjust_srh. The Header Ext. Length field contains the SRH
len rounded to 8 bytes (a padding TLV can be inserted to ensure the 8-bytes
boundary). When adding/deleting TLVs within the BPF program, the SRH may
temporary be in an invalid state where its length cannot be rounded to 8
bytes without remainder, hence the need to store the length in bytes
separately to keep track of it. Again, a final SRH modified by a BPF
program which doesn’t respect the 8-bytes boundary will be discarded as
it will be considered as invalid.

Finally, a fourth helper is provided, bpf_lwt_push_encap, which is
available from the LWT BPF IN hook, but not from the seg6local BPF one.
This helper allows to encapsulate a Segment Routing Header (either with
a new outer IPv6 header, or by inlining it directly in the existing IPv6
header) into a non-SRv6 packet. This helper is required if we want to
offer the possibility to dynamically encapsulate a SRH for non-SRv6 packet,
as the BPF seg6local hook only works on traffic already containing a SRH.
This is the BPF equivalent of the seg6 LWT infrastructure, which achieves
the same purpose but with a static SRH per route.

Signed-off-by: Mathieu Xhonneux <m.xhonneux@gmail.com>
Acked-by: David Lebrun <dlebrun@google.com>
---
 include/net/seg6_local.h |   5 +
 include/uapi/linux/bpf.h |  56 +++++++++-
 net/core/filter.c        | 263 +++++++++++++++++++++++++++++++++++++++++++----
 3 files changed, 302 insertions(+), 22 deletions(-)

diff --git a/include/net/seg6_local.h b/include/net/seg6_local.h
index 57498b23085d..4eae7adfca34 100644
--- a/include/net/seg6_local.h
+++ b/include/net/seg6_local.h
@@ -21,4 +21,9 @@
 extern int seg6_lookup_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
 			       u32 tbl_id);
 
+struct seg6_bpf_srh_state {
+	bool valid;
+	u16 hdrlen;
+};
+
 #endif
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 18b7c510c511..f2679c29e353 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -729,6 +729,50 @@ union bpf_attr {
  *     @flags: reserved for future use
  *     Return: SK_PASS
  *
+ * int lwt_push_encap(skb, type, hdr, len)
+ *     Push an encapsulation header on top of current packet.
+ *     @type: type of header to push :
+ *          - BPF_LWT_ENCAP_SEG6 (push an IPv6 Segment Routing Header, struct
+ *                    ipv6_sr_hdr, the helper will add the outer IPv6 header)
+ *          - BPF_LWT_ENCAP_SEG6_INLINE (push an IPv6 Segment Routing Header,
+ *                       struct ipv6_sr_hdr, inside the existing IPv6 header)
+ *     @hdr: pointer where to copy the header from
+ *     @len: size of hdr in bytes
+ *     Return: 0 on success or negative error
+ *
+ * int lwt_seg6_store_bytes(skb, offset, from, len)
+ *     Store bytes into the outermost Segment Routing header of an IPv6 header.
+ *     Only the flags, tag and TLVs can be modified.
+ *     @skb: pointer to skb
+ *     @offset: offset within packet from skb->data
+ *     @from: pointer where to copy bytes from
+ *     @len: number of bytes to store into packet
+ *     Return: 0 on success or negative error
+ *
+ * int lwt_seg6_adjust_srh(skb, offset, delta)
+ *     Adjust the size allocated to TLVs in the outermost IPv6 Segment Routing
+ *     Header (grow if delta > 0, else shrink)
+ *     @skb: pointer to skb
+ *     @offset: offset within packet from skb->data where SRH will grow/shrink,
+ *              only offsets after the segments are accepted
+ *     @delta: a positive/negative integer
+ *     Return: 0 on success or negative on error
+ *
+ * int lwt_seg6_action(skb, action, param, param_len)
+ *     Apply a IPv6 Segment Routing action on a packet with an IPv6 Segment
+ *     Routing Header.
+ *     @action:
+ *              - End.X: SEG6_LOCAL_ACTION_END_X
+ *                                           (type of param: struct in6_addr)
+ *              - End.T: SEG6_LOCAL_ACTION_END_T
+ *                                           (type of param: int)
+ *              - End.B6: SEG6_LOCAL_ACTION_END_B6
+ *                                           (type of param: struct ipv6_sr_hdr)
+ *              - End.B6.Encap: SEG6_LOCAL_ACTION_END_B6_ENCAP
+ *                                           (type of param: struct ipv6_sr_hdr)
+ *     @param: pointer to the parameter required by the action
+ *     @param_len: length of param in bytes
+ *     Return: 0 on success or negative error
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -794,7 +838,11 @@ union bpf_attr {
 	FN(msg_redirect_map),		\
 	FN(msg_apply_bytes),		\
 	FN(msg_cork_bytes),		\
-	FN(msg_pull_data),
+	FN(msg_pull_data),		\
+	FN(lwt_push_encap),		\
+	FN(lwt_seg6_store_bytes),	\
+	FN(lwt_seg6_adjust_srh),	\
+	FN(lwt_seg6_action),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
@@ -852,6 +900,12 @@ enum bpf_adj_room_mode {
 	BPF_ADJ_ROOM_NET,
 };
 
+/* Encapsulation type for BPF_FUNC_lwt_push_encap helper. */
+enum bpf_lwt_encap_mode {
+	BPF_LWT_ENCAP_SEG6,
+	BPF_LWT_ENCAP_SEG6_INLINE
+};
+
 /* user accessible mirror of in-kernel sk_buff.
  * new fields can only be added to the end of this structure
  */
diff --git a/net/core/filter.c b/net/core/filter.c
index c86f03fd9ea5..71019593a246 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -57,6 +57,10 @@
 #include <net/busy_poll.h>
 #include <net/tcp.h>
 #include <linux/bpf_trace.h>
+#include <net/ipv6.h>
+#include <linux/seg6_local.h>
+#include <net/seg6.h>
+#include <net/seg6_local.h>
 
 /**
  *	sk_filter_trim_cap - run a packet through a socket filter
@@ -3013,27 +3017,6 @@ static const struct bpf_func_proto bpf_xdp_redirect_map_proto = {
 	.arg3_type      = ARG_ANYTHING,
 };
 
-bool bpf_helper_changes_pkt_data(void *func)
-{
-	if (func == bpf_skb_vlan_push ||
-	    func == bpf_skb_vlan_pop ||
-	    func == bpf_skb_store_bytes ||
-	    func == bpf_skb_change_proto ||
-	    func == bpf_skb_change_head ||
-	    func == bpf_skb_change_tail ||
-	    func == bpf_skb_adjust_room ||
-	    func == bpf_skb_pull_data ||
-	    func == bpf_clone_redirect ||
-	    func == bpf_l3_csum_replace ||
-	    func == bpf_l4_csum_replace ||
-	    func == bpf_xdp_adjust_head ||
-	    func == bpf_xdp_adjust_meta ||
-	    func == bpf_msg_pull_data)
-		return true;
-
-	return false;
-}
-
 static unsigned long bpf_skb_copy(void *dst_buff, const void *skb,
 				  unsigned long off, unsigned long len)
 {
@@ -3597,6 +3580,244 @@ static const struct bpf_func_proto bpf_sock_ops_cb_flags_set_proto = {
 	.arg2_type	= ARG_ANYTHING,
 };
 
+int bpf_push_seg6_encap(struct sk_buff *skb, u32 type, void *hdr, u32 len)
+{
+	int err;
+	struct ipv6_sr_hdr *srh = (struct ipv6_sr_hdr *)hdr;
+
+	if (!seg6_validate_srh(srh, len))
+		return -EINVAL;
+
+	switch (type) {
+	case BPF_LWT_ENCAP_SEG6_INLINE:
+		if (skb->protocol != htons(ETH_P_IPV6))
+			return -EBADMSG;
+
+		err = seg6_do_srh_inline(skb, srh);
+		break;
+	case BPF_LWT_ENCAP_SEG6:
+		skb_reset_inner_headers(skb);
+		skb->encapsulation = 1;
+		err = seg6_do_srh_encap(skb, srh, IPPROTO_IPV6);
+		break;
+	default:
+		return -EINVAL;
+	}
+	if (err)
+		return err;
+
+	ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
+	skb_set_transport_header(skb, sizeof(struct ipv6hdr));
+
+	return seg6_lookup_nexthop(skb, NULL, 0);
+}
+
+BPF_CALL_4(bpf_lwt_push_encap, struct sk_buff *, skb, u32, type, void *, hdr,
+	   u32, len)
+{
+	switch (type) {
+	case BPF_LWT_ENCAP_SEG6:
+	case BPF_LWT_ENCAP_SEG6_INLINE:
+		return bpf_push_seg6_encap(skb, type, hdr, len);
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct bpf_func_proto bpf_lwt_push_encap_proto = {
+	.func		= bpf_lwt_push_encap,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_ANYTHING,
+	.arg3_type	= ARG_PTR_TO_MEM,
+	.arg4_type	= ARG_CONST_SIZE
+};
+
+BPF_CALL_4(bpf_lwt_seg6_store_bytes, struct sk_buff *, skb, u32, offset,
+	   const void *, from, u32, len)
+{
+	struct seg6_bpf_srh_state *srh_state = (struct seg6_bpf_srh_state *)
+					       &skb->cb;
+	void *srh_tlvs, *srh_end, *ptr;
+	struct ipv6_sr_hdr *srh;
+	int srhoff = 0;
+
+	if (ipv6_find_hdr(skb, &srhoff, IPPROTO_ROUTING, NULL, NULL) < 0)
+		return -EINVAL;
+
+	srh = (struct ipv6_sr_hdr *)(skb->data + srhoff);
+	srh_tlvs = (void *)((char *)srh + ((srh->first_segment + 1) << 4));
+	srh_end = (void *)((char *)srh + sizeof(*srh) + srh_state->hdrlen);
+
+	ptr = skb->data + offset;
+	if (ptr >= srh_tlvs && ptr + len <= srh_end)
+		srh_state->valid = 0;
+	else if (ptr < (void *)&srh->flags ||
+		 ptr + len > (void *)&srh->segments)
+		return -EFAULT;
+
+	if (unlikely(bpf_try_make_writable(skb, offset + len)))
+		return -EFAULT;
+
+	memcpy(ptr, from, len);
+	return 0;
+}
+
+static const struct bpf_func_proto bpf_lwt_seg6_store_bytes_proto = {
+	.func		= bpf_lwt_seg6_store_bytes,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_ANYTHING,
+	.arg3_type	= ARG_PTR_TO_MEM,
+	.arg4_type	= ARG_CONST_SIZE
+};
+
+BPF_CALL_4(bpf_lwt_seg6_action, struct sk_buff *, skb,
+	   u32, action, void *, param, u32, param_len)
+{
+	struct seg6_bpf_srh_state *srh_state = (struct seg6_bpf_srh_state *)
+					       &skb->cb;
+	struct ipv6_sr_hdr *srh;
+	int srhoff = 0;
+	int err;
+
+	if (ipv6_find_hdr(skb, &srhoff, IPPROTO_ROUTING, NULL, NULL) < 0)
+		return -EINVAL;
+	srh = (struct ipv6_sr_hdr *)(skb->data + srhoff);
+
+	if (!srh_state->valid) {
+		if (unlikely((srh_state->hdrlen & 7) != 0))
+			return -EBADMSG;
+
+		srh->hdrlen = (u8)(srh_state->hdrlen >> 3);
+		if (unlikely(!seg6_validate_srh(srh, (srh->hdrlen + 1) << 3)))
+			return -EBADMSG;
+
+		srh_state->valid = 1;
+	}
+
+	switch (action) {
+	case SEG6_LOCAL_ACTION_END_X:
+		if (param_len != sizeof(struct in6_addr))
+			return -EINVAL;
+		return seg6_lookup_nexthop(skb, (struct in6_addr *)param, 0);
+	case SEG6_LOCAL_ACTION_END_T:
+		if (param_len != sizeof(int))
+			return -EINVAL;
+		return seg6_lookup_nexthop(skb, NULL, *(int *)param);
+	case SEG6_LOCAL_ACTION_END_B6:
+		err = bpf_push_seg6_encap(skb, BPF_LWT_ENCAP_SEG6_INLINE,
+					  param, param_len);
+		if (!err)
+			srh_state->hdrlen =
+				((struct ipv6_sr_hdr *)param)->hdrlen << 3;
+		return err;
+	case SEG6_LOCAL_ACTION_END_B6_ENCAP:
+		err = bpf_push_seg6_encap(skb, BPF_LWT_ENCAP_SEG6,
+					  param, param_len);
+		if (!err)
+			srh_state->hdrlen =
+				((struct ipv6_sr_hdr *)param)->hdrlen << 3;
+		return err;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct bpf_func_proto bpf_lwt_seg6_action_proto = {
+	.func		= bpf_lwt_seg6_action,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_ANYTHING,
+	.arg3_type	= ARG_PTR_TO_MEM,
+	.arg4_type	= ARG_CONST_SIZE
+};
+
+BPF_CALL_3(bpf_lwt_seg6_adjust_srh, struct sk_buff *, skb, u32, offset,
+	   s32, len)
+{
+	struct seg6_bpf_srh_state *srh_state = (struct seg6_bpf_srh_state *)
+					       &skb->cb;
+
+	void *srh_end, *srh_tlvs, *ptr;
+	struct ipv6_sr_hdr *srh;
+	struct ipv6hdr *hdr;
+	int srhoff = 0;
+	int ret;
+
+	if (ipv6_find_hdr(skb, &srhoff, IPPROTO_ROUTING, NULL, NULL) < 0)
+		return -EINVAL;
+	srh = (struct ipv6_sr_hdr *)(skb->data + srhoff);
+
+	srh_tlvs = (void *)((unsigned char *)srh + sizeof(*srh) +
+			((srh->first_segment + 1) << 4));
+	srh_end = (void *)((unsigned char *)srh + sizeof(*srh) +
+			srh_state->hdrlen);
+	ptr = skb->data + offset;
+
+	if (unlikely(ptr < srh_tlvs || ptr > srh_end))
+		return -EFAULT;
+	if (unlikely(len < 0 && (void *)((char *)ptr - len) > srh_end))
+		return -EFAULT;
+
+	if (len > 0) {
+		ret = skb_cow_head(skb, len);
+		if (unlikely(ret < 0))
+			return ret;
+
+		ret = bpf_skb_net_hdr_push(skb, offset, len);
+	} else {
+		ret = bpf_skb_net_hdr_pop(skb, offset, -1 * len);
+	}
+	if (unlikely(ret < 0))
+		return ret;
+
+	hdr = (struct ipv6hdr *)skb->data;
+	hdr->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
+
+	bpf_compute_data_pointers(skb);
+	srh_state->hdrlen += len;
+	srh_state->valid = 0;
+	return 0;
+}
+
+static const struct bpf_func_proto bpf_lwt_seg6_adjust_srh_proto = {
+	.func		= bpf_lwt_seg6_adjust_srh,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_ANYTHING,
+	.arg3_type	= ARG_ANYTHING,
+};
+
+bool bpf_helper_changes_pkt_data(void *func)
+{
+	if (func == bpf_skb_vlan_push ||
+	    func == bpf_skb_vlan_pop ||
+	    func == bpf_skb_store_bytes ||
+	    func == bpf_skb_change_proto ||
+	    func == bpf_skb_change_head ||
+	    func == bpf_skb_change_tail ||
+	    func == bpf_skb_adjust_room ||
+	    func == bpf_skb_pull_data ||
+	    func == bpf_clone_redirect ||
+	    func == bpf_l3_csum_replace ||
+	    func == bpf_l4_csum_replace ||
+	    func == bpf_xdp_adjust_head ||
+	    func == bpf_xdp_adjust_meta ||
+	    func == bpf_msg_pull_data ||
+	    func == bpf_lwt_push_encap ||
+	    func == bpf_lwt_seg6_store_bytes ||
+	    func == bpf_lwt_seg6_adjust_srh
+	    )
+		return true;
+
+	return false;
+}
+
 static const struct bpf_func_proto *
 bpf_base_func_proto(enum bpf_func_id func_id)
 {
-- 
2.16.1

^ permalink raw reply related	[flat|nested] 12+ messages in thread
* [PATCH net-next RFC 3/5] bpf: Split lwt inout verifier structures
  2018-03-23 10:15 [PATCH net-next RFC 0/5] ipv6: sr: introduce seg6local End.BPF action Mathieu Xhonneux
  2018-03-23 10:16 ` [PATCH net-next RFC 1/5] ipv6: sr: export function lookup_nexthop Mathieu Xhonneux
  2018-03-23 10:16 ` [PATCH next-next RFC 2/5] bpf: Add IPv6 Segment Routing helpers Mathieu Xhonneux
@ 2018-03-23 10:16 ` Mathieu Xhonneux
  2018-03-23 10:16 ` [PATCH net-next RFC 4/5] ipv6: sr: Add seg6local action End.BPF Mathieu Xhonneux
                   ` (2 subsequent siblings)
  5 siblings, 0 replies; 12+ messages in thread
From: Mathieu Xhonneux @ 2018-03-23 10:16 UTC (permalink / raw)
  To: netdev; +Cc: dlebrun

The new bpf_lwt_push_encap helper should only be accessible within the
LWT BPF IN hook, and not the OUT one, as this may lead to a skb under
panic.

At the moment, both LWT BPF IN and OUT share the same list of helpers,
whose calls are authorized by the verifier. This patch separates the
verifier ops for the IN and OUT hooks, and allows the IN hook to call the
bpf_lwt_push_encap helper.

This patch is also the occasion to put all lwt_*_func_proto functions
together for clarity. At the moment, socks_op_func_proto is in the middle
of lwt_inout_func_proto and lwt_xmit_func_proto.

Signed-off-by: Mathieu Xhonneux <m.xhonneux@gmail.com>
Acked-by: David Lebrun <dlebrun@google.com>
---
 include/linux/bpf_types.h |  4 +--
 net/core/filter.c         | 85 ++++++++++++++++++++++++++++++-----------------
 2 files changed, 56 insertions(+), 33 deletions(-)

diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
index 5e2e8a49fb21..0f8f2525da9b 100644
--- a/include/linux/bpf_types.h
+++ b/include/linux/bpf_types.h
@@ -8,8 +8,8 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_SCHED_ACT, tc_cls_act)
 BPF_PROG_TYPE(BPF_PROG_TYPE_XDP, xdp)
 BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SKB, cg_skb)
 BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SOCK, cg_sock)
-BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_IN, lwt_inout)
-BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_OUT, lwt_inout)
+BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_IN, lwt_in)
+BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_OUT, lwt_out)
 BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_XMIT, lwt_xmit)
 BPF_PROG_TYPE(BPF_PROG_TYPE_SOCK_OPS, sock_ops)
 BPF_PROG_TYPE(BPF_PROG_TYPE_SK_SKB, sk_skb)
diff --git a/net/core/filter.c b/net/core/filter.c
index 71019593a246..741dd352937d 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3965,33 +3965,6 @@ xdp_func_proto(enum bpf_func_id func_id)
 	}
 }
 
-static const struct bpf_func_proto *
-lwt_inout_func_proto(enum bpf_func_id func_id)
-{
-	switch (func_id) {
-	case BPF_FUNC_skb_load_bytes:
-		return &bpf_skb_load_bytes_proto;
-	case BPF_FUNC_skb_pull_data:
-		return &bpf_skb_pull_data_proto;
-	case BPF_FUNC_csum_diff:
-		return &bpf_csum_diff_proto;
-	case BPF_FUNC_get_cgroup_classid:
-		return &bpf_get_cgroup_classid_proto;
-	case BPF_FUNC_get_route_realm:
-		return &bpf_get_route_realm_proto;
-	case BPF_FUNC_get_hash_recalc:
-		return &bpf_get_hash_recalc_proto;
-	case BPF_FUNC_perf_event_output:
-		return &bpf_skb_event_output_proto;
-	case BPF_FUNC_get_smp_processor_id:
-		return &bpf_get_smp_processor_id_proto;
-	case BPF_FUNC_skb_under_cgroup:
-		return &bpf_skb_under_cgroup_proto;
-	default:
-		return bpf_base_func_proto(func_id);
-	}
-}
-
 static const struct bpf_func_proto *
 	sock_ops_func_proto(enum bpf_func_id func_id)
 {
@@ -4049,6 +4022,44 @@ static const struct bpf_func_proto *sk_skb_func_proto(enum bpf_func_id func_id)
 	}
 }
 
+static const struct bpf_func_proto *
+lwt_out_func_proto(enum bpf_func_id func_id)
+{
+	switch (func_id) {
+	case BPF_FUNC_skb_load_bytes:
+		return &bpf_skb_load_bytes_proto;
+	case BPF_FUNC_skb_pull_data:
+		return &bpf_skb_pull_data_proto;
+	case BPF_FUNC_csum_diff:
+		return &bpf_csum_diff_proto;
+	case BPF_FUNC_get_cgroup_classid:
+		return &bpf_get_cgroup_classid_proto;
+	case BPF_FUNC_get_route_realm:
+		return &bpf_get_route_realm_proto;
+	case BPF_FUNC_get_hash_recalc:
+		return &bpf_get_hash_recalc_proto;
+	case BPF_FUNC_perf_event_output:
+		return &bpf_skb_event_output_proto;
+	case BPF_FUNC_get_smp_processor_id:
+		return &bpf_get_smp_processor_id_proto;
+	case BPF_FUNC_skb_under_cgroup:
+		return &bpf_skb_under_cgroup_proto;
+	default:
+		return bpf_base_func_proto(func_id);
+	}
+}
+
+static const struct bpf_func_proto *
+lwt_in_func_proto(enum bpf_func_id func_id)
+{
+	switch (func_id) {
+	case BPF_FUNC_lwt_push_encap:
+		return &bpf_lwt_push_encap_proto;
+	default:
+		return lwt_out_func_proto(func_id);
+	}
+}
+
 static const struct bpf_func_proto *
 lwt_xmit_func_proto(enum bpf_func_id func_id)
 {
@@ -4080,7 +4091,9 @@ lwt_xmit_func_proto(enum bpf_func_id func_id)
 	case BPF_FUNC_set_hash_invalid:
 		return &bpf_set_hash_invalid_proto;
 	default:
-		return lwt_inout_func_proto(func_id);
+		return lwt_out_func_proto(func_id);
+	}
+}
 	}
 }
 
@@ -5302,13 +5315,23 @@ const struct bpf_prog_ops cg_skb_prog_ops = {
 	.test_run		= bpf_prog_test_run_skb,
 };
 
-const struct bpf_verifier_ops lwt_inout_verifier_ops = {
-	.get_func_proto		= lwt_inout_func_proto,
+const struct bpf_verifier_ops lwt_in_verifier_ops = {
+	.get_func_proto		= lwt_in_func_proto,
+	.is_valid_access	= lwt_is_valid_access,
+	.convert_ctx_access	= bpf_convert_ctx_access,
+};
+
+const struct bpf_prog_ops lwt_in_prog_ops = {
+	.test_run		= bpf_prog_test_run_skb,
+};
+
+const struct bpf_verifier_ops lwt_out_verifier_ops = {
+	.get_func_proto		= lwt_out_func_proto,
 	.is_valid_access	= lwt_is_valid_access,
 	.convert_ctx_access	= bpf_convert_ctx_access,
 };
 
-const struct bpf_prog_ops lwt_inout_prog_ops = {
+const struct bpf_prog_ops lwt_out_prog_ops = {
 	.test_run		= bpf_prog_test_run_skb,
 };
 
-- 
2.16.1

^ permalink raw reply related	[flat|nested] 12+ messages in thread
* [PATCH net-next RFC 4/5] ipv6: sr: Add seg6local action End.BPF
  2018-03-23 10:15 [PATCH net-next RFC 0/5] ipv6: sr: introduce seg6local End.BPF action Mathieu Xhonneux
                   ` (2 preceding siblings ...)
  2018-03-23 10:16 ` [PATCH net-next RFC 3/5] bpf: Split lwt inout verifier structures Mathieu Xhonneux
@ 2018-03-23 10:16 ` Mathieu Xhonneux
  2018-03-23 10:16 ` [PATCH net-next RFC 5/5] selftests/bpf: test for seg6local End.BPF action Mathieu Xhonneux
  2018-03-30 23:03 ` [PATCH net-next RFC 0/5] ipv6: sr: introduce " Alexei Starovoitov
  5 siblings, 0 replies; 12+ messages in thread
From: Mathieu Xhonneux @ 2018-03-23 10:16 UTC (permalink / raw)
  To: netdev; +Cc: dlebrun

This patch adds the End.BPF action to the LWT seg6local infrastructure.
This action works like any other seg6local End action, meaning that an IPv6
header with SRH is needed, whose DA has to be equal to the SID of the
action. It will also advance the SRH to the next segment, the BPF program
doesn’t have to take care of this.

Since the BPF program may not be a source of instability in the kernel, it
is important to ensure that the integrity of the packet is maintained
before yielding it back to the IPv6 layer. The hook hence keeps track if
the SRH has been altered through the helpers, and re-validates its
content if needed with seg6_validate_srh. The state kept for validation is
stored in skb->cb, read and write access to it from the BPF program is
prohibited. The BPF program is not allowed to directly write into the
packet, and only some fields of the SRH can be altered through the helper
bpf_lwt_seg6_store_bytes.

Performances profiling has shown that the SRH re-validation doesn’t induce
a significant overhead. If the altered SRH is deemed as invalid, the packet
is dropped.

This validation is also done before executing any action through
bpf_lwt_seg6_action, and won’t be performed again if the SRH isn’t modified
after calling the action.

The BPF program may return 3 types of return codes :
    - BPF_OK: the End.BPF action will look up the next destination through
             seg6_lookup_nexthop.
    - BPF_REDIRECT: if an action has been executed through the
          bpf_lwt_seg6_action helper, the BPF program should return this
          value, as the skb destination is already set and the default
          lookup shouldn’t be performed.
    - BPF_DROP : the packet will be dropped.

Signed-off-by: Mathieu Xhonneux <m.xhonneux@gmail.com>
Acked-by: David Lebrun <dlebrun@google.com>
---
 include/linux/bpf_types.h       |   1 +
 include/uapi/linux/bpf.h        |   1 +
 include/uapi/linux/seg6_local.h |   3 +
 kernel/bpf/verifier.c           |   1 +
 net/core/filter.c               |  37 ++++++++++
 net/ipv6/seg6_local.c           | 150 +++++++++++++++++++++++++++++++++++++++-
 6 files changed, 190 insertions(+), 3 deletions(-)

diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
index 0f8f2525da9b..92bc613a3b59 100644
--- a/include/linux/bpf_types.h
+++ b/include/linux/bpf_types.h
@@ -11,6 +11,7 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SOCK, cg_sock)
 BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_IN, lwt_in)
 BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_OUT, lwt_out)
 BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_XMIT, lwt_xmit)
+BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_SEG6LOCAL, lwt_seg6local)
 BPF_PROG_TYPE(BPF_PROG_TYPE_SOCK_OPS, sock_ops)
 BPF_PROG_TYPE(BPF_PROG_TYPE_SK_SKB, sk_skb)
 BPF_PROG_TYPE(BPF_PROG_TYPE_SK_MSG, sk_msg)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index f2679c29e353..2eeea4c4cc7f 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -134,6 +134,7 @@ enum bpf_prog_type {
 	BPF_PROG_TYPE_SK_SKB,
 	BPF_PROG_TYPE_CGROUP_DEVICE,
 	BPF_PROG_TYPE_SK_MSG,
+	BPF_PROG_TYPE_LWT_SEG6LOCAL,
 };
 
 enum bpf_attach_type {
diff --git a/include/uapi/linux/seg6_local.h b/include/uapi/linux/seg6_local.h
index ef2d8c3e76c1..aadcc11fb918 100644
--- a/include/uapi/linux/seg6_local.h
+++ b/include/uapi/linux/seg6_local.h
@@ -25,6 +25,7 @@ enum {
 	SEG6_LOCAL_NH6,
 	SEG6_LOCAL_IIF,
 	SEG6_LOCAL_OIF,
+	SEG6_LOCAL_BPF,
 	__SEG6_LOCAL_MAX,
 };
 #define SEG6_LOCAL_MAX (__SEG6_LOCAL_MAX - 1)
@@ -59,6 +60,8 @@ enum {
 	SEG6_LOCAL_ACTION_END_AS	= 13,
 	/* forward to SR-unaware VNF with masquerading */
 	SEG6_LOCAL_ACTION_END_AM	= 14,
+	/* custom BPF action */
+	SEG6_LOCAL_ACTION_END_BPF	= 15,
 
 	__SEG6_LOCAL_ACTION_MAX,
 };
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index e9f7c20691c1..3c645ad33ac7 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1239,6 +1239,7 @@ static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
 	switch (env->prog->type) {
 	case BPF_PROG_TYPE_LWT_IN:
 	case BPF_PROG_TYPE_LWT_OUT:
+	case BPF_PROG_TYPE_LWT_SEG6LOCAL:
 		/* dst_input() and dst_output() can't write for now */
 		if (t == BPF_WRITE)
 			return false;
diff --git a/net/core/filter.c b/net/core/filter.c
index 741dd352937d..4b46d09dcddc 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4094,6 +4094,19 @@ lwt_xmit_func_proto(enum bpf_func_id func_id)
 		return lwt_out_func_proto(func_id);
 	}
 }
+
+static const struct bpf_func_proto *
+lwt_seg6local_func_proto(enum bpf_func_id func_id)
+{
+	switch (func_id) {
+	case BPF_FUNC_lwt_seg6_store_bytes:
+		return &bpf_lwt_seg6_store_bytes_proto;
+	case BPF_FUNC_lwt_seg6_action:
+		return &bpf_lwt_seg6_action_proto;
+	case BPF_FUNC_lwt_seg6_adjust_srh:
+		return &bpf_lwt_seg6_adjust_srh_proto;
+	default:
+		return lwt_out_func_proto(func_id);
 	}
 }
 
@@ -4198,6 +4211,20 @@ static bool lwt_is_valid_access(int off, int size,
 	return bpf_skb_is_valid_access(off, size, type, info);
 }
 
+static bool lwt_seg6local_is_valid_access(int off, int size,
+					  enum bpf_access_type type,
+					  struct bpf_insn_access_aux *info)
+{
+	switch (off) {
+	case bpf_ctx_range_till(struct __sk_buff, cb[0], cb[4]):
+		return false;
+	default:
+		break;
+	}
+
+	return lwt_is_valid_access(off, size, type, info);
+}
+
 static bool sock_filter_is_valid_access(int off, int size,
 					enum bpf_access_type type,
 					struct bpf_insn_access_aux *info)
@@ -5346,6 +5373,16 @@ const struct bpf_prog_ops lwt_xmit_prog_ops = {
 	.test_run		= bpf_prog_test_run_skb,
 };
 
+const struct bpf_verifier_ops lwt_seg6local_verifier_ops = {
+	.get_func_proto		= lwt_seg6local_func_proto,
+	.is_valid_access	= lwt_seg6local_is_valid_access,
+	.convert_ctx_access	= bpf_convert_ctx_access,
+};
+
+const struct bpf_prog_ops lwt_seg6local_prog_ops = {
+	.test_run		= bpf_prog_test_run_skb,
+};
+
 const struct bpf_verifier_ops cg_sock_verifier_ops = {
 	.get_func_proto		= sock_filter_func_proto,
 	.is_valid_access	= sock_filter_is_valid_access,
diff --git a/net/ipv6/seg6_local.c b/net/ipv6/seg6_local.c
index e9b23fb924ad..4805b7d404ed 100644
--- a/net/ipv6/seg6_local.c
+++ b/net/ipv6/seg6_local.c
@@ -1,8 +1,9 @@
 /*
  *  SR-IPv6 implementation
  *
- *  Author:
+ *  Authors:
  *  David Lebrun <david.lebrun@uclouvain.be>
+ *  eBPF support: Mathieu Xhonneux <m.xhonneux@gmail.com>
  *
  *
  *  This program is free software; you can redistribute it and/or
@@ -32,6 +33,7 @@
 #endif
 #include <net/seg6_local.h>
 #include <linux/etherdevice.h>
+#include <linux/bpf.h>
 
 struct seg6_local_lwt;
 
@@ -42,6 +44,11 @@ struct seg6_action_desc {
 	int static_headroom;
 };
 
+struct bpf_lwt_prog {
+	struct bpf_prog *prog;
+	char *name;
+};
+
 struct seg6_local_lwt {
 	int action;
 	struct ipv6_sr_hdr *srh;
@@ -50,6 +57,7 @@ struct seg6_local_lwt {
 	struct in6_addr nh6;
 	int iif;
 	int oif;
+	struct bpf_lwt_prog bpf;
 
 	int headroom;
 	struct seg6_action_desc *desc;
@@ -449,6 +457,61 @@ static int input_action_end_b6_encap(struct sk_buff *skb,
 	return err;
 }
 
+static int input_action_end_bpf(struct sk_buff *skb,
+				struct seg6_local_lwt *slwt)
+{
+	struct seg6_bpf_srh_state *srh_state = (struct seg6_bpf_srh_state *)
+					       &skb->cb;
+	struct ipv6_sr_hdr *srh;
+	int srhoff = 0;
+	int ret;
+
+	srh = get_and_validate_srh(skb);
+	if (!srh)
+		goto drop;
+
+	advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
+	srh_state->hdrlen = srh->hdrlen << 3;
+	srh_state->valid = 1;
+
+	rcu_read_lock();
+	bpf_compute_data_pointers(skb);
+	ret = bpf_prog_run_save_cb(slwt->bpf.prog, skb);
+	rcu_read_unlock();
+
+	switch (ret) {
+	case BPF_OK:
+	case BPF_REDIRECT:
+		break;
+	case BPF_DROP:
+		goto drop;
+	default:
+		pr_warn_once("bpf-seg6local: Illegal return value %u\n", ret);
+		goto drop;
+	}
+
+	if (unlikely((srh_state->hdrlen & 7) != 0))
+		goto drop;
+
+	if (ipv6_find_hdr(skb, &srhoff, IPPROTO_ROUTING, NULL, NULL) < 0)
+		goto drop;
+	srh = (struct ipv6_sr_hdr *)(skb->data + srhoff);
+	srh->hdrlen = (u8)(srh_state->hdrlen >> 3);
+
+	if (!srh_state->valid &&
+	    unlikely(!seg6_validate_srh(srh, (srh->hdrlen + 1) << 3)))
+		goto drop;
+
+	if (ret != BPF_REDIRECT)
+		seg6_lookup_nexthop(skb, NULL, 0);
+
+	return dst_input(skb);
+
+drop:
+	kfree_skb(skb);
+	return -EINVAL;
+}
+
 static struct seg6_action_desc seg6_action_table[] = {
 	{
 		.action		= SEG6_LOCAL_ACTION_END,
@@ -495,7 +558,13 @@ static struct seg6_action_desc seg6_action_table[] = {
 		.attrs		= (1 << SEG6_LOCAL_SRH),
 		.input		= input_action_end_b6_encap,
 		.static_headroom	= sizeof(struct ipv6hdr),
-	}
+	},
+	{
+		.action		= SEG6_LOCAL_ACTION_END_BPF,
+		.attrs		= (1 << SEG6_LOCAL_BPF),
+		.input		= input_action_end_bpf,
+	},
+
 };
 
 static struct seg6_action_desc *__get_action_desc(int action)
@@ -540,6 +609,7 @@ static const struct nla_policy seg6_local_policy[SEG6_LOCAL_MAX + 1] = {
 				    .len = sizeof(struct in6_addr) },
 	[SEG6_LOCAL_IIF]	= { .type = NLA_U32 },
 	[SEG6_LOCAL_OIF]	= { .type = NLA_U32 },
+	[SEG6_LOCAL_BPF]	= { .type = NLA_NESTED },
 };
 
 static int parse_nla_srh(struct nlattr **attrs, struct seg6_local_lwt *slwt)
@@ -717,6 +787,71 @@ static int cmp_nla_oif(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
 	return 0;
 }
 
+#define MAX_PROG_NAME 256
+static const struct nla_policy bpf_prog_policy[LWT_BPF_PROG_MAX + 1] = {
+	[LWT_BPF_PROG_FD]   = { .type = NLA_U32, },
+	[LWT_BPF_PROG_NAME] = { .type = NLA_NUL_STRING,
+				.len = MAX_PROG_NAME },
+};
+
+static int parse_nla_bpf(struct nlattr **attrs, struct seg6_local_lwt *slwt)
+{
+	struct nlattr *tb[LWT_BPF_PROG_MAX + 1];
+	struct bpf_prog *p;
+	int ret;
+	u32 fd;
+
+	ret = nla_parse_nested(tb, LWT_BPF_PROG_MAX, attrs[SEG6_LOCAL_BPF],
+			       bpf_prog_policy, NULL);
+	if (ret < 0)
+		return ret;
+
+	if (!tb[LWT_BPF_PROG_FD] || !tb[LWT_BPF_PROG_NAME])
+		return -EINVAL;
+
+	slwt->bpf.name = nla_memdup(tb[LWT_BPF_PROG_NAME], GFP_KERNEL);
+	if (!slwt->bpf.name)
+		return -ENOMEM;
+
+	fd = nla_get_u32(tb[LWT_BPF_PROG_FD]);
+	p = bpf_prog_get_type(fd, BPF_PROG_TYPE_LWT_SEG6LOCAL);
+	if (IS_ERR(p))
+		return PTR_ERR(p);
+
+	slwt->bpf.prog = p;
+
+	return 0;
+}
+
+static int put_nla_bpf(struct sk_buff *skb, struct seg6_local_lwt *slwt)
+{
+	struct nlattr *nest;
+
+	if (!slwt->bpf.prog)
+		return 0;
+
+	nest = nla_nest_start(skb, SEG6_LOCAL_BPF);
+	if (!nest)
+		return -EMSGSIZE;
+
+	if (slwt->bpf.name &&
+	    nla_put_string(skb, LWT_BPF_PROG_NAME, slwt->bpf.name))
+		return -EMSGSIZE;
+
+	return nla_nest_end(skb, nest);
+}
+
+static int cmp_nla_bpf(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
+{
+	if (!a->bpf.name && !b->bpf.name)
+		return 0;
+
+	if (!a->bpf.name || !b->bpf.name)
+		return 1;
+
+	return strcmp(a->bpf.name, b->bpf.name);
+}
+
 struct seg6_action_param {
 	int (*parse)(struct nlattr **attrs, struct seg6_local_lwt *slwt);
 	int (*put)(struct sk_buff *skb, struct seg6_local_lwt *slwt);
@@ -747,6 +882,11 @@ static struct seg6_action_param seg6_action_params[SEG6_LOCAL_MAX + 1] = {
 	[SEG6_LOCAL_OIF]	= { .parse = parse_nla_oif,
 				    .put = put_nla_oif,
 				    .cmp = cmp_nla_oif },
+
+	[SEG6_LOCAL_BPF]	= { .parse = parse_nla_bpf,
+				    .put = put_nla_bpf,
+				    .cmp = cmp_nla_bpf },
+
 };
 
 static int parse_nla_action(struct nlattr **attrs, struct seg6_local_lwt *slwt)
@@ -795,7 +935,6 @@ static int seg6_local_build_state(struct nlattr *nla, unsigned int family,
 
 	err = nla_parse_nested(tb, SEG6_LOCAL_MAX, nla, seg6_local_policy,
 			       extack);
-
 	if (err < 0)
 		return err;
 
@@ -884,6 +1023,11 @@ static int seg6_local_get_encap_size(struct lwtunnel_state *lwt)
 	if (attrs & (1 << SEG6_LOCAL_OIF))
 		nlsize += nla_total_size(4);
 
+	if (attrs & (1 << SEG6_LOCAL_BPF))
+		nlsize += nla_total_size(sizeof(struct nlattr)) +
+		       nla_total_size(MAX_PROG_NAME) +
+		       nla_total_size(4);
+
 	return nlsize;
 }
 
-- 
2.16.1

^ permalink raw reply related	[flat|nested] 12+ messages in thread
* [PATCH net-next RFC 5/5] selftests/bpf: test for seg6local End.BPF action
  2018-03-23 10:15 [PATCH net-next RFC 0/5] ipv6: sr: introduce seg6local End.BPF action Mathieu Xhonneux
                   ` (3 preceding siblings ...)
  2018-03-23 10:16 ` [PATCH net-next RFC 4/5] ipv6: sr: Add seg6local action End.BPF Mathieu Xhonneux
@ 2018-03-23 10:16 ` Mathieu Xhonneux
  2018-03-30 23:03 ` [PATCH net-next RFC 0/5] ipv6: sr: introduce " Alexei Starovoitov
  5 siblings, 0 replies; 12+ messages in thread
From: Mathieu Xhonneux @ 2018-03-23 10:16 UTC (permalink / raw)
  To: netdev; +Cc: dlebrun

Add a new test for the seg6local End.BPF action. The following helpers
are also tested :

- bpf_lwt_push_encap within the LWT BPF IN hook
- bpf_lwt_seg6_action
- bpf_lwt_seg6_adjust_srh
- bpf_lwt_seg6_store_bytes

A chain of End.BPF actions is built. The SRH is injected through a LWT
BPF IN hook before the chain. Each End.BPF action validates the previous
one, otherwise the packet is dropped.
The test succeeds if the last node in the chain receives the packet and
the UDP datagram contained can be retrieved from userspace.

Signed-off-by: Mathieu Xhonneux <m.xhonneux@gmail.com>
---
 tools/include/uapi/linux/bpf.h                    |  58 ++-
 tools/testing/selftests/bpf/Makefile              |   5 +-
 tools/testing/selftests/bpf/bpf_helpers.h         |  12 +
 tools/testing/selftests/bpf/test_lwt_seg6local.c  | 438 ++++++++++++++++++++++
 tools/testing/selftests/bpf/test_lwt_seg6local.sh | 140 +++++++
 5 files changed, 650 insertions(+), 3 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/test_lwt_seg6local.c
 create mode 100755 tools/testing/selftests/bpf/test_lwt_seg6local.sh

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index d245c41213ac..2eeea4c4cc7f 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -134,6 +134,7 @@ enum bpf_prog_type {
 	BPF_PROG_TYPE_SK_SKB,
 	BPF_PROG_TYPE_CGROUP_DEVICE,
 	BPF_PROG_TYPE_SK_MSG,
+	BPF_PROG_TYPE_LWT_SEG6LOCAL,
 };
 
 enum bpf_attach_type {
@@ -729,6 +730,50 @@ union bpf_attr {
  *     @flags: reserved for future use
  *     Return: SK_PASS
  *
+ * int lwt_push_encap(skb, type, hdr, len)
+ *     Push an encapsulation header on top of current packet.
+ *     @type: type of header to push :
+ *          - BPF_LWT_ENCAP_SEG6 (push an IPv6 Segment Routing Header, struct
+ *                    ipv6_sr_hdr, the helper will add the outer IPv6 header)
+ *          - BPF_LWT_ENCAP_SEG6_INLINE (push an IPv6 Segment Routing Header,
+ *                       struct ipv6_sr_hdr, inside the existing IPv6 header)
+ *     @hdr: pointer where to copy the header from
+ *     @len: size of hdr in bytes
+ *     Return: 0 on success or negative error
+ *
+ * int lwt_seg6_store_bytes(skb, offset, from, len)
+ *     Store bytes into the outermost Segment Routing header of an IPv6 header.
+ *     Only the flags, tag and TLVs can be modified.
+ *     @skb: pointer to skb
+ *     @offset: offset within packet from skb->data
+ *     @from: pointer where to copy bytes from
+ *     @len: number of bytes to store into packet
+ *     Return: 0 on success or negative error
+ *
+ * int lwt_seg6_adjust_srh(skb, offset, delta)
+ *     Adjust the size allocated to TLVs in the outermost IPv6 Segment Routing
+ *     Header (grow if delta > 0, else shrink)
+ *     @skb: pointer to skb
+ *     @offset: offset within packet from skb->data where SRH will grow/shrink,
+ *              only offsets after the segments are accepted
+ *     @delta: a positive/negative integer
+ *     Return: 0 on success or negative on error
+ *
+ * int lwt_seg6_action(skb, action, param, param_len)
+ *     Apply a IPv6 Segment Routing action on a packet with an IPv6 Segment
+ *     Routing Header.
+ *     @action:
+ *              - End.X: SEG6_LOCAL_ACTION_END_X
+ *                                           (type of param: struct in6_addr)
+ *              - End.T: SEG6_LOCAL_ACTION_END_T
+ *                                           (type of param: int)
+ *              - End.B6: SEG6_LOCAL_ACTION_END_B6
+ *                                           (type of param: struct ipv6_sr_hdr)
+ *              - End.B6.Encap: SEG6_LOCAL_ACTION_END_B6_ENCAP
+ *                                           (type of param: struct ipv6_sr_hdr)
+ *     @param: pointer to the parameter required by the action
+ *     @param_len: length of param in bytes
+ *     Return: 0 on success or negative error
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -794,7 +839,11 @@ union bpf_attr {
 	FN(msg_redirect_map),		\
 	FN(msg_apply_bytes),		\
 	FN(msg_cork_bytes),		\
-	FN(msg_pull_data),
+	FN(msg_pull_data),		\
+	FN(lwt_push_encap),		\
+	FN(lwt_seg6_store_bytes),	\
+	FN(lwt_seg6_adjust_srh),	\
+	FN(lwt_seg6_action),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
@@ -837,6 +886,7 @@ enum bpf_func_id {
 /* BPF_FUNC_skb_set_tunnel_key flags. */
 #define BPF_F_ZERO_CSUM_TX		(1ULL << 1)
 #define BPF_F_DONT_FRAGMENT		(1ULL << 2)
+#define BPF_F_SEQ_NUMBER		(1ULL << 3)
 
 /* BPF_FUNC_perf_event_output, BPF_FUNC_perf_event_read and
  * BPF_FUNC_perf_event_read_value flags.
@@ -851,6 +901,12 @@ enum bpf_adj_room_mode {
 	BPF_ADJ_ROOM_NET,
 };
 
+/* Encapsulation type for BPF_FUNC_lwt_push_encap helper. */
+enum bpf_lwt_encap_mode {
+	BPF_LWT_ENCAP_SEG6,
+	BPF_LWT_ENCAP_SEG6_INLINE
+};
+
 /* user accessible mirror of in-kernel sk_buff.
  * new fields can only be added to the end of this structure
  */
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index f35fb02bdf56..95c6bb8548a3 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -30,14 +30,15 @@ TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test
 	sockmap_verdict_prog.o dev_cgroup.o sample_ret0.o test_tracepoint.o \
 	test_l4lb_noinline.o test_xdp_noinline.o test_stacktrace_map.o \
 	sample_map_ret0.o test_tcpbpf_kern.o test_stacktrace_build_id.o \
-	sockmap_tcp_msg_prog.o
+	sockmap_tcp_msg_prog.o test_lwt_seg6local.o
 
 # Order correspond to 'make run_tests' order
 TEST_PROGS := test_kmod.sh \
 	test_libbpf.sh \
 	test_xdp_redirect.sh \
 	test_xdp_meta.sh \
-	test_offload.py
+	test_offload.py \
+	test_lwt_seg6local.sh
 
 # Compile but not part of 'make run_tests'
 TEST_GEN_PROGS_EXTENDED = test_libbpf_open
diff --git a/tools/testing/selftests/bpf/bpf_helpers.h b/tools/testing/selftests/bpf/bpf_helpers.h
index 7cae376d8d0c..9a89a2a4cea8 100644
--- a/tools/testing/selftests/bpf/bpf_helpers.h
+++ b/tools/testing/selftests/bpf/bpf_helpers.h
@@ -94,6 +94,18 @@ static int (*bpf_msg_cork_bytes)(void *ctx, int len) =
 	(void *) BPF_FUNC_msg_cork_bytes;
 static int (*bpf_msg_pull_data)(void *ctx, int start, int end, int flags) =
 	(void *) BPF_FUNC_msg_pull_data;
+static int (*bpf_lwt_push_encap)(void *ctx, unsigned int type, void *hdr,
+				 unsigned int len) =
+	(void *) BPF_FUNC_lwt_push_encap;
+static int (*bpf_lwt_seg6_store_bytes)(void *ctx, unsigned int offset,
+				       void *from, unsigned int len) =
+	(void *) BPF_FUNC_lwt_seg6_store_bytes;
+static int (*bpf_lwt_seg6_action)(void *ctx, unsigned int action, void *param,
+				  unsigned int param_len) =
+	(void *) BPF_FUNC_lwt_seg6_action;
+static int (*bpf_lwt_seg6_adjust_srh)(void *ctx, unsigned int offset,
+				      unsigned int len) =
+	(void *) BPF_FUNC_lwt_seg6_adjust_srh;
 
 /* llvm builtin functions that eBPF C program may use to
  * emit BPF_LD_ABS and BPF_LD_IND instructions
diff --git a/tools/testing/selftests/bpf/test_lwt_seg6local.c b/tools/testing/selftests/bpf/test_lwt_seg6local.c
new file mode 100644
index 000000000000..d752bc1fe81c
--- /dev/null
+++ b/tools/testing/selftests/bpf/test_lwt_seg6local.c
@@ -0,0 +1,438 @@
+#include <stddef.h>
+#include <inttypes.h>
+#include <errno.h>
+#include <linux/seg6_local.h>
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+#include "bpf_endian.h"
+
+#define bpf_printk(fmt, ...)				\
+({							\
+	char ____fmt[] = fmt;				\
+	bpf_trace_printk(____fmt, sizeof(____fmt),	\
+			##__VA_ARGS__);			\
+})
+
+/* Packet parsing state machine helpers. */
+#define cursor_advance(_cursor, _len) \
+	({ void *_tmp = _cursor; _cursor += _len; _tmp; })
+
+#define SR6_FLAG_ALERT (1 << 4)
+
+#define htonll(x) ((bpf_htonl(1)) == 1 ? (x) : ((uint64_t)bpf_htonl((x) & \
+				0xFFFFFFFF) << 32) | bpf_htonl((x) >> 32))
+#define ntohll(x) ((bpf_ntohl(1)) == 1 ? (x) : ((uint64_t)bpf_ntohl((x) & \
+				0xFFFFFFFF) << 32) | bpf_ntohl((x) >> 32))
+#define BPF_PACKET_HEADER __attribute__((packed))
+
+struct ip6_t {
+	unsigned int ver:4;
+	unsigned int priority:8;
+	unsigned int flow_label:20;
+	unsigned short payload_len;
+	unsigned char next_header;
+	unsigned char hop_limit;
+	unsigned long long src_hi;
+	unsigned long long src_lo;
+	unsigned long long dst_hi;
+	unsigned long long dst_lo;
+} BPF_PACKET_HEADER;
+
+struct ip6_addr_t {
+	unsigned long long hi;
+	unsigned long long lo;
+} BPF_PACKET_HEADER;
+
+struct ip6_srh_t {
+	unsigned char nexthdr;
+	unsigned char hdrlen;
+	unsigned char type;
+	unsigned char segments_left;
+	unsigned char first_segment;
+	unsigned char flags;
+	unsigned short tag;
+
+	struct ip6_addr_t segments[0];
+} BPF_PACKET_HEADER;
+
+struct sr6_tlv_t {
+	unsigned char type;
+	unsigned char len;
+	unsigned char value[0];
+} BPF_PACKET_HEADER;
+
+__attribute__((always_inline)) struct ip6_srh_t *get_srh(struct __sk_buff *skb)
+{
+	void *cursor, *data_end;
+	struct ip6_srh_t *srh;
+	struct ip6_t *ip;
+	uint8_t *ipver;
+
+	data_end = (void *)(long)skb->data_end;
+	cursor = (void *)(long)skb->data;
+	ipver = (uint8_t *)cursor;
+
+	if ((void *)ipver + sizeof(*ipver) > data_end)
+		return NULL;
+
+	if ((*ipver >> 4) != 6)
+		return NULL;
+
+	ip = cursor_advance(cursor, sizeof(*ip));
+	if ((void *)ip + sizeof(*ip) > data_end)
+		return NULL;
+
+	if (ip->next_header != 43)
+		return NULL;
+
+	srh = cursor_advance(cursor, sizeof(*srh));
+	if ((void *)srh + sizeof(*srh) > data_end)
+		return NULL;
+
+	if (srh->type != 4)
+		return NULL;
+
+	return srh;
+}
+
+__attribute__((always_inline))
+int update_tlv_pad(struct __sk_buff *skb, uint32_t new_pad,
+		   uint32_t old_pad, uint32_t pad_off)
+{
+	int err;
+
+	if (new_pad != old_pad) {
+		err = bpf_lwt_seg6_adjust_srh(skb, pad_off,
+					  (int) new_pad - (int) old_pad);
+		if (err)
+			return err;
+	}
+
+	if (new_pad > 0) {
+		char pad_tlv_buf[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+					0, 0, 0};
+		struct sr6_tlv_t *pad_tlv = (struct sr6_tlv_t *) pad_tlv_buf;
+
+		pad_tlv->type = SR6_TLV_PADDING;
+		pad_tlv->len = new_pad - 2;
+
+		err = bpf_lwt_seg6_store_bytes(skb, pad_off,
+					       (void *)pad_tlv_buf, new_pad);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+__attribute__((always_inline))
+int is_valid_tlv_boundary(struct __sk_buff *skb, struct ip6_srh_t *srh,
+			  uint32_t *tlv_off, uint32_t *pad_size,
+			  uint32_t *pad_off)
+{
+	uint32_t srh_off, cur_off;
+	int offset_valid = 0;
+	int err;
+
+	srh_off = (char *)srh - (char *)(long)skb->data;
+	// cur_off = end of segments, start of possible TLVs
+	cur_off = srh_off + sizeof(*srh) +
+		sizeof(struct ip6_addr_t) * (srh->first_segment + 1);
+
+	*pad_off = 0;
+
+	// we can only go as far as ~10 TLVs due to the BPF max stack size
+	#pragma clang loop unroll(full)
+	for (int i = 0; i < 10; i++) {
+		struct sr6_tlv_t tlv;
+
+		if (cur_off == *tlv_off)
+			offset_valid = 1;
+
+		if (cur_off >= srh_off + ((srh->hdrlen + 1) << 3))
+			break;
+
+		err = bpf_skb_load_bytes(skb, cur_off, &tlv, sizeof(tlv));
+		if (err)
+			return err;
+
+		if (tlv.type == SR6_TLV_PADDING) {
+			*pad_size = tlv.len + sizeof(tlv);
+			*pad_off = cur_off;
+
+			if (*tlv_off == srh_off) {
+				*tlv_off = cur_off;
+				offset_valid = 1;
+			}
+			break;
+
+		} else if (tlv.type == SR6_TLV_HMAC) {
+			break;
+		}
+
+		cur_off += sizeof(tlv) + tlv.len;
+	} // we reached the padding or HMAC TLVs, or the end of the SRH
+
+	if (*pad_off == 0)
+		*pad_off = cur_off;
+
+	if (*tlv_off == -1)
+		*tlv_off = cur_off;
+	else if (!offset_valid)
+		return -EINVAL;
+
+	return 0;
+}
+
+__attribute__((always_inline))
+int add_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh, uint32_t tlv_off,
+	    struct sr6_tlv_t *itlv, uint8_t tlv_size)
+{
+	uint32_t srh_off = (char *)srh - (char *)(long)skb->data;
+	uint8_t len_remaining, new_pad;
+	uint32_t pad_off = 0;
+	uint32_t pad_size = 0;
+	uint32_t partial_srh_len;
+	int err;
+
+	if (tlv_off != -1)
+		tlv_off += srh_off;
+
+	if (itlv->type == SR6_TLV_PADDING || itlv->type == SR6_TLV_HMAC)
+		return -EINVAL;
+
+	err = is_valid_tlv_boundary(skb, srh, &tlv_off, &pad_size, &pad_off);
+	if (err)
+		return err;
+
+	err = bpf_lwt_seg6_adjust_srh(skb, tlv_off, sizeof(*itlv) + itlv->len);
+	if (err)
+		return err;
+
+	err = bpf_lwt_seg6_store_bytes(skb, tlv_off, (void *)itlv, tlv_size);
+	if (err)
+		return err;
+
+	// the following can't be moved inside update_tlv_pad because the
+	// bpf verifier has some issues with it
+	pad_off += sizeof(*itlv) + itlv->len;
+	partial_srh_len = pad_off - srh_off;
+	len_remaining = partial_srh_len % 8;
+	new_pad = 8 - len_remaining;
+
+	if (new_pad == 1) // cannot pad for 1 byte only
+		new_pad = 9;
+	else if (new_pad == 8)
+		new_pad = 0;
+
+	return update_tlv_pad(skb, new_pad, pad_size, pad_off);
+}
+
+__attribute__((always_inline))
+int delete_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh,
+	       uint32_t tlv_off)
+{
+	uint32_t srh_off = (char *)srh - (char *)(long)skb->data;
+	uint8_t len_remaining, new_pad;
+	uint32_t partial_srh_len;
+	uint32_t pad_off = 0;
+	uint32_t pad_size = 0;
+	struct sr6_tlv_t tlv;
+	int err;
+
+	tlv_off += srh_off;
+
+	err = is_valid_tlv_boundary(skb, srh, &tlv_off, &pad_size, &pad_off);
+	if (err)
+		return err;
+
+	err = bpf_skb_load_bytes(skb, tlv_off, &tlv, sizeof(tlv));
+	if (err)
+		return err;
+
+	err = bpf_lwt_seg6_adjust_srh(skb, tlv_off, -(sizeof(tlv) + tlv.len));
+	if (err)
+		return err;
+
+	pad_off -= sizeof(tlv) + tlv.len;
+	partial_srh_len = pad_off - srh_off;
+	len_remaining = partial_srh_len % 8;
+	new_pad = 8 - len_remaining;
+	if (new_pad == 1) // cannot pad for 1 byte only
+		new_pad = 9;
+	else if (new_pad == 8)
+		new_pad = 0;
+
+	return update_tlv_pad(skb, new_pad, pad_size, pad_off);
+}
+
+__attribute__((always_inline))
+int has_egr_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh)
+{
+	int tlv_offset = sizeof(struct ip6_t) + sizeof(struct ip6_srh_t) +
+		((srh->first_segment + 1) << 4);
+	struct sr6_tlv_t tlv;
+
+	if (bpf_skb_load_bytes(skb, tlv_offset, &tlv, sizeof(struct sr6_tlv_t)))
+		return 0;
+
+	if (tlv.type == SR6_TLV_EGRESS && tlv.len == 18) {
+		struct ip6_addr_t egr_addr;
+
+		if (bpf_skb_load_bytes(skb, tlv_offset + 4, &egr_addr, 16))
+			return 0;
+
+		// check if egress TLV value is correct
+		if (ntohll(egr_addr.hi) == 0xfd00000000000000 &&
+				ntohll(egr_addr.lo) == 0x4)
+			return 1;
+	}
+
+	return 0;
+}
+
+// This function will push a SRH with segments fd00::1, fd00::2, fd00::3,
+// fd00::4
+SEC("encap_srh")
+int __encap_srh(struct __sk_buff *skb)
+{
+	bpf_printk("got pkt\n");
+	unsigned long long hi = 0xfd00000000000000;
+	struct ip6_addr_t *seg;
+	struct ip6_srh_t *srh;
+	char srh_buf[72]; // room for 4 segments
+	int err;
+
+	srh = (struct ip6_srh_t *)srh_buf;
+	srh->nexthdr = 0;
+	srh->hdrlen = 8;
+	srh->type = 4;
+	srh->segments_left = 3;
+	srh->first_segment = 3;
+	srh->flags = 0;
+	srh->tag = 0;
+
+	seg = (struct ip6_addr_t *)((char *)srh + sizeof(*srh));
+
+	#pragma clang loop unroll(full)
+	for (unsigned long long lo = 0; lo < 4; lo++) {
+		seg->lo = htonll(4 - lo);
+		seg->hi = htonll(hi);
+		seg = (struct ip6_addr_t *)((char *)seg + sizeof(*seg));
+	}
+
+	err = bpf_lwt_push_encap(skb, 0, (void *)srh, sizeof(srh_buf));
+	if (err)
+		return BPF_DROP;
+
+	return BPF_REDIRECT;
+}
+
+// Add an Egress TLV fc00::4, add the flag A,
+// and apply End.X action to fc42::1
+SEC("add_egr_x")
+int __add_egr_x(struct __sk_buff *skb)
+{
+	unsigned long long hi = 0xfc42000000000000;
+	unsigned long long lo = 0x1;
+	struct ip6_srh_t *srh = get_srh(skb);
+	uint8_t new_flags = SR6_FLAG_ALERT;
+	struct ip6_addr_t addr;
+	int err, offset;
+
+	if (srh == NULL)
+		return BPF_DROP;
+
+	uint8_t tlv[20] = {2, 18, 0, 0, 0xfd, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
+			   0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x4};
+
+	err = add_tlv(skb, srh, (srh->hdrlen+1) << 3,
+		      (struct sr6_tlv_t *)&tlv, 20);
+	if (err)
+		return BPF_DROP;
+
+	offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, flags);
+	err = bpf_lwt_seg6_store_bytes(skb, offset,
+				       (void *)&new_flags, sizeof(new_flags));
+	if (err)
+		return BPF_DROP;
+
+	addr.lo = htonll(lo);
+	addr.hi = htonll(hi);
+	err = bpf_lwt_seg6_action(skb, SEG6_LOCAL_ACTION_END_X,
+				  (void *)&addr, sizeof(addr));
+	if (err)
+		return BPF_DROP;
+	return BPF_REDIRECT;
+}
+
+// Pop the Egress TLV, reset the flags, change the tag 2442 and finally do a
+// simple End action
+SEC("pop_egr")
+int __pop_egr(struct __sk_buff *skb)
+{
+	struct ip6_srh_t *srh = get_srh(skb);
+	uint16_t new_tag = bpf_htons(2442);
+	uint8_t new_flags = 0;
+	int err, offset;
+
+	if (srh == NULL)
+		return BPF_DROP;
+
+	if (srh->flags != SR6_FLAG_ALERT)
+		return BPF_DROP;
+
+	if (srh->hdrlen != 11) // 4 segments + Egress TLV + Padding TLV
+		return BPF_DROP;
+
+	if (!has_egr_tlv(skb, srh))
+		return BPF_DROP;
+
+	err = delete_tlv(skb, srh, 8 + (srh->first_segment + 1) * 16);
+	if (err)
+		return BPF_DROP;
+
+	offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, flags);
+	if (bpf_lwt_seg6_store_bytes(skb, offset, (void *)&new_flags,
+				     sizeof(new_flags)))
+		return BPF_DROP;
+
+	offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, tag);
+	if (bpf_lwt_seg6_store_bytes(skb, offset, (void *)&new_tag,
+				     sizeof(new_tag)))
+		return BPF_DROP;
+
+	return BPF_OK;
+}
+
+// Inspect if the Egress TLV and flag have been removed, if the tag is correct,
+// then apply a End.T action to reach the last segment
+SEC("inspect_t")
+int __inspect_t(struct __sk_buff *skb)
+{
+	struct ip6_srh_t *srh = get_srh(skb);
+	int table = 117;
+	int err;
+
+	if (srh == NULL)
+		return BPF_DROP;
+
+	if (srh->flags != 0)
+		return BPF_DROP;
+
+	if (srh->tag != bpf_htons(2442))
+		return BPF_DROP;
+
+	if (srh->hdrlen != 8) // 4 segments
+		return BPF_DROP;
+
+	err = bpf_lwt_seg6_action(skb, SEG6_LOCAL_ACTION_END_T,
+				  (void *)&table, sizeof(table));
+
+	if (err)
+		return BPF_DROP;
+
+	return BPF_REDIRECT;
+}
+
+char __license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/test_lwt_seg6local.sh b/tools/testing/selftests/bpf/test_lwt_seg6local.sh
new file mode 100755
index 000000000000..1c77994b5e71
--- /dev/null
+++ b/tools/testing/selftests/bpf/test_lwt_seg6local.sh
@@ -0,0 +1,140 @@
+#!/bin/bash
+# Connects 6 network namespaces through veths.
+# Each NS may have different IPv6 global scope addresses :
+#   NS1 ---- NS2 ---- NS3 ---- NS4 ---- NS5 ---- NS6
+# fb00::1           fd00::1  fd00::2  fd00::3  fb00::6
+#                   fc42::1           fd00::4
+#
+# All IPv6 packets going to fb00::/16 through NS2 will be encapsulated in a
+# IPv6 header with a Segment Routing Header, with segments :
+# 	fd00::1 -> fd00::2 -> fd00::3 -> fd00::4
+#
+# 3 fd00::/16 IPv6 addresses are binded to seg6local End.BPF actions :
+# - fd00::1 : add a TLV, change the flags and apply a End.X action to fc42::1
+# - fd00::2 : remove the TLV, change the flags, add a tag
+# - fd00::3 : apply an End.T action to fd00::4, through routing table 117
+#
+# fd00::4 is a simple Segment Routing node decapsulating the inner IPv6 packet.
+# Each End.BPF action will validate the operations applied on the SRH by the
+# previous BPF program in the chain, otherwise the packet is dropped.
+#
+# An UDP datagram is sent from fb00::1 to fb00::6. The test succeeds if this
+# datagram can be read on NS6 when binding to fb00::6.
+
+TMP_FILE="/tmp/selftest_lwt_seg6local.txt"
+
+cleanup()
+{
+	if [ "$?" = "0" ]; then
+		echo "selftests: test_lwt_seg6local [PASS]";
+	else
+		echo "selftests: test_lwt_seg6local [FAILED]";
+	fi
+
+	set +e
+	ip netns del ns1 2> /dev/null
+	ip netns del ns2 2> /dev/null
+	ip netns del ns3 2> /dev/null
+	ip netns del ns4 2> /dev/null
+	ip netns del ns5 2> /dev/null
+	ip netns del ns6 2> /dev/null
+	rm -f $TMP_FILE
+}
+
+set -e
+
+ip netns add ns1
+ip netns add ns2
+ip netns add ns3
+ip netns add ns4
+ip netns add ns5
+ip netns add ns6
+
+trap cleanup 0 2 3 6 9
+
+ip link add veth1 type veth peer name veth2
+ip link add veth3 type veth peer name veth4
+ip link add veth5 type veth peer name veth6
+ip link add veth7 type veth peer name veth8
+ip link add veth9 type veth peer name veth10
+
+ip link set veth1 netns ns1
+ip link set veth2 netns ns2
+ip link set veth3 netns ns2
+ip link set veth4 netns ns3
+ip link set veth5 netns ns3
+ip link set veth6 netns ns4
+ip link set veth7 netns ns4
+ip link set veth8 netns ns5
+ip link set veth9 netns ns5
+ip link set veth10 netns ns6
+
+ip netns exec ns1 ip link set dev veth1 up
+ip netns exec ns2 ip link set dev veth2 up
+ip netns exec ns2 ip link set dev veth3 up
+ip netns exec ns3 ip link set dev veth4 up
+ip netns exec ns3 ip link set dev veth5 up
+ip netns exec ns4 ip link set dev veth6 up
+ip netns exec ns4 ip link set dev veth7 up
+ip netns exec ns5 ip link set dev veth8 up
+ip netns exec ns5 ip link set dev veth9 up
+ip netns exec ns6 ip link set dev veth10 up
+ip netns exec ns6 ip link set dev lo up
+
+# All link scope addresses and routes required between veths
+ip netns exec ns1 ip -6 addr add fb00::12/16 dev veth1 scope link
+ip netns exec ns1 ip -6 route add fb00::21 dev veth1 scope link
+ip netns exec ns2 ip -6 addr add fb00::21/16 dev veth2 scope link
+ip netns exec ns2 ip -6 addr add fb00::34/16 dev veth3 scope link
+ip netns exec ns2 ip -6 route add fb00::43 dev veth3 scope link
+ip netns exec ns3 ip -6 route add fb00::65 dev veth5 scope link
+ip netns exec ns3 ip -6 addr add fb00::43/16 dev veth4 scope link
+ip netns exec ns3 ip -6 addr add fb00::56/16 dev veth5 scope link
+ip netns exec ns4 ip -6 addr add fb00::65/16 dev veth6 scope link
+ip netns exec ns4 ip -6 addr add fb00::78/16 dev veth7 scope link
+ip netns exec ns4 ip -6 route add fb00::87 dev veth7 scope link
+ip netns exec ns5 ip -6 addr add fb00::87/16 dev veth8 scope link
+ip netns exec ns5 ip -6 addr add fb00::910/16 dev veth9 scope link
+ip netns exec ns5 ip -6 route add fb00::109 dev veth9 scope link
+ip netns exec ns5 ip -6 route add fb00::109 table 117 dev veth9 scope link
+ip netns exec ns6 ip -6 addr add fb00::109/16 dev veth10 scope link
+
+ip netns exec ns1 ip -6 addr add fb00::1/16 dev lo
+ip netns exec ns1 ip -6 route add fb00::6 dev veth1 via fb00::21
+
+ip netns exec ns2 ip -6 route add fb00::6 encap bpf in obj test_lwt_seg6local.o sec encap_srh dev veth2
+ip netns exec ns2 ip -6 route add fd00::1 dev veth3 via fb00::43 scope link
+
+ip netns exec ns3 ip -6 route add fc42::1 dev veth5 via fb00::65
+ip netns exec ns3 ip -6 route add fd00::1 encap seg6local action End.BPF obj test_lwt_seg6local.o sec add_egr_x dev veth4
+
+ip netns exec ns4 ip -6 route add fd00::2 encap seg6local action End.BPF obj test_lwt_seg6local.o sec pop_egr dev veth6
+ip netns exec ns4 ip -6 addr add fc42::1 dev lo
+ip netns exec ns4 ip -6 route add fd00::3 dev veth7 via fb00::87
+
+ip netns exec ns5 ip -6 route add fd00::4 table 117 dev veth9 via fb00::109
+ip netns exec ns5 ip -6 route add fd00::3 encap seg6local action End.BPF obj test_lwt_seg6local.o sec inspect_t dev veth8
+
+ip netns exec ns6 ip -6 addr add fb00::6/16 dev lo
+ip netns exec ns6 ip -6 addr add fd00::4/16 dev lo
+
+ip netns exec ns1 sysctl net.ipv6.conf.all.forwarding=1 > /dev/null
+ip netns exec ns2 sysctl net.ipv6.conf.all.forwarding=1 > /dev/null
+ip netns exec ns3 sysctl net.ipv6.conf.all.forwarding=1 > /dev/null
+ip netns exec ns4 sysctl net.ipv6.conf.all.forwarding=1 > /dev/null
+ip netns exec ns5 sysctl net.ipv6.conf.all.forwarding=1 > /dev/null
+
+ip netns exec ns6 sysctl net.ipv6.conf.all.seg6_enabled=1 > /dev/null
+ip netns exec ns6 sysctl net.ipv6.conf.lo.seg6_enabled=1 > /dev/null
+ip netns exec ns6 sysctl net.ipv6.conf.veth10.seg6_enabled=1 > /dev/null
+
+ip netns exec ns6 nc -l -6 -u -d 7330 > $TMP_FILE &
+ip netns exec ns1 bash -c "echo 'foobar' | nc -w0 -6 -u -p 2121 -s fb00::1 fb00::6 7330"
+sleep 5 # wait enough time to ensure the UDP datagram arrived to the last segment
+kill -INT $!
+
+if [[ $(< $TMP_FILE) != "foobar" ]]; then
+	exit 1
+fi
+
+exit 0
-- 
2.16.1

^ permalink raw reply related	[flat|nested] 12+ messages in thread
* Re: [PATCH net-next RFC 0/5] ipv6: sr: introduce seg6local End.BPF action
  2018-03-23 10:15 [PATCH net-next RFC 0/5] ipv6: sr: introduce seg6local End.BPF action Mathieu Xhonneux
                   ` (4 preceding siblings ...)
  2018-03-23 10:16 ` [PATCH net-next RFC 5/5] selftests/bpf: test for seg6local End.BPF action Mathieu Xhonneux
@ 2018-03-30 23:03 ` Alexei Starovoitov
  2018-04-03 11:16   ` Mathieu Xhonneux
  5 siblings, 1 reply; 12+ messages in thread
From: Alexei Starovoitov @ 2018-03-30 23:03 UTC (permalink / raw)
  To: Mathieu Xhonneux; +Cc: netdev, dlebrun, Daniel Borkmann

On Fri, Mar 23, 2018 at 10:15:59AM +0000, Mathieu Xhonneux wrote:
> As of Linux 4.14, it is possible to define advanced local processing for
> IPv6 packets with a Segment Routing Header through the seg6local LWT
> infrastructure. This LWT implements the network programming principles
> defined in the IETF “SRv6 Network Programming” draft.
> 
> The implemented operations are generic, and it would be very interesting to
> be able to implement user-specific seg6local actions, without having to
> modify the kernel directly. To do so, this patchset adds an End.BPF action
> to seg6local, powered by some specific Segment Routing-related helpers,
> which provide SR functionalities that can be applied on the packet. This
> BPF hook would then allow to implement specific actions at native kernel
> speed such as OAM features, advanced SR SDN policies, SRv6 actions like
> Segment Routing Header (SRH) encapsulation depending on the content of
> the packet, etc ... 
> 
> This patchset is divided in 5 patches, whose main features are :
> 
> - A new seg6local action End.BPF with the corresponding new BPF program
>   type BPF_PROG_TYPE_LWT_SEG6LOCAL. Such attached BPF program can be
>   passed to the LWT seg6local through netlink, the same way as the LWT
>   BPF hook operates.
> - 3 new BPF helpers for the seg6local BPF hook, allowing to edit/grow/
>   shrink a SRH and apply on a packet some of the generic SRv6 actions.
> - 1 new BPF helper for the LWT BPF IN hook, allowing to add a SRH through
>   encapsulation (via IPv6 encapsulation or inlining if the packet contains
>   already an IPv6 header).
> 
> As this patchset adds a new LWT BPF hook, I took into account the result of
> the discussions when the LWT BPF infrastructure got merged. Hence, the
> seg6local BPF hook doesn’t allow write access to skb->data directly, only
> the SRH can be modified through specific helpers, which ensures that the
> integrity of the packet is maintained.
> More details are available in the related patches messages.
> 
> The performances of this BPF hook have been assessed with the BPF JIT
> enabled on a Intel Xeon X3440 processors with 4 cores and 8 threads
> clocked at 2.53 GHz. No throughput losses are noted with the seg6local
> BPF hook when the BPF program does nothing (440kpps). Adding a 8-bytes
> TLV (1 call each to bpf_lwt_seg6_adjust_srh and bpf_lwt_seg6_store_bytes)
> drops the throughput to 410kpps, and inlining a SRH via
> bpf_lwt_seg6_action drops the throughput to 420kpps.
> All throughputs are stable.
> 
> Any comments on the patchset are welcome.

I've looked through the patches and everything looks very good.
Feel free to resubmit without RFC tag.

In patch 2 I was a bit concerned that:
+       struct seg6_bpf_srh_state *srh_state = (struct seg6_bpf_srh_state *)
+                                              &skb->cb;
would not collide with other users of skb->cb, but it seems the way
the hook is placed such usage should always be valid.
Would be good to add a comment describing the situation.

Looks like somewhat odd 'End.BPF' name comes from similar names in SRv6 draft.
Do you plan to disclose such End.BPF action in the draft as well?

Thanks

^ permalink raw reply	[flat|nested] 12+ messages in thread
* Re: [PATCH net-next RFC 0/5] ipv6: sr: introduce seg6local End.BPF action
  2018-03-30 23:03 ` [PATCH net-next RFC 0/5] ipv6: sr: introduce " Alexei Starovoitov
@ 2018-04-03 11:16   ` Mathieu Xhonneux
  2018-04-03 13:40     ` David Lebrun
  0 siblings, 1 reply; 12+ messages in thread
From: Mathieu Xhonneux @ 2018-04-03 11:16 UTC (permalink / raw)
  To: Alexei Starovoitov; +Cc: netdev, David Lebrun, Daniel Borkmann

2018-03-31 1:03 GMT+02:00 Alexei Starovoitov <alexei.starovoitov@gmail.com>:
>
> On Fri, Mar 23, 2018 at 10:15:59AM +0000, Mathieu Xhonneux wrote:
> > As of Linux 4.14, it is possible to define advanced local processing for
> > IPv6 packets with a Segment Routing Header through the seg6local LWT
> > infrastructure. This LWT implements the network programming principles
> > defined in the IETF “SRv6 Network Programming” draft.
> >
> > The implemented operations are generic, and it would be very interesting to
> > be able to implement user-specific seg6local actions, without having to
> > modify the kernel directly. To do so, this patchset adds an End.BPF action
> > to seg6local, powered by some specific Segment Routing-related helpers,
> > which provide SR functionalities that can be applied on the packet. This
> > BPF hook would then allow to implement specific actions at native kernel
> > speed such as OAM features, advanced SR SDN policies, SRv6 actions like
> > Segment Routing Header (SRH) encapsulation depending on the content of
> > the packet, etc ...
> >
> > This patchset is divided in 5 patches, whose main features are :
> >
> > - A new seg6local action End.BPF with the corresponding new BPF program
> >   type BPF_PROG_TYPE_LWT_SEG6LOCAL. Such attached BPF program can be
> >   passed to the LWT seg6local through netlink, the same way as the LWT
> >   BPF hook operates.
> > - 3 new BPF helpers for the seg6local BPF hook, allowing to edit/grow/
> >   shrink a SRH and apply on a packet some of the generic SRv6 actions.
> > - 1 new BPF helper for the LWT BPF IN hook, allowing to add a SRH through
> >   encapsulation (via IPv6 encapsulation or inlining if the packet contains
> >   already an IPv6 header).
> >
> > As this patchset adds a new LWT BPF hook, I took into account the result of
> > the discussions when the LWT BPF infrastructure got merged. Hence, the
> > seg6local BPF hook doesn’t allow write access to skb->data directly, only
> > the SRH can be modified through specific helpers, which ensures that the
> > integrity of the packet is maintained.
> > More details are available in the related patches messages.
> >
> > The performances of this BPF hook have been assessed with the BPF JIT
> > enabled on a Intel Xeon X3440 processors with 4 cores and 8 threads
> > clocked at 2.53 GHz. No throughput losses are noted with the seg6local
> > BPF hook when the BPF program does nothing (440kpps). Adding a 8-bytes
> > TLV (1 call each to bpf_lwt_seg6_adjust_srh and bpf_lwt_seg6_store_bytes)
> > drops the throughput to 410kpps, and inlining a SRH via
> > bpf_lwt_seg6_action drops the throughput to 420kpps.
> > All throughputs are stable.
> >
> > Any comments on the patchset are welcome.
>
> I've looked through the patches and everything looks very good.
> Feel free to resubmit without RFC tag.
Thanks, I will do this as soon as net-next opens.

>
> In patch 2 I was a bit concerned that:
> +       struct seg6_bpf_srh_state *srh_state = (struct seg6_bpf_srh_state *)
> +                                              &skb->cb;
> would not collide with other users of skb->cb, but it seems the way
> the hook is placed such usage should always be valid.
> Would be good to add a comment describing the situation.
Yes, it's indeed a little hack, but this should be OK since the IPv6 layer does
not use the cb field. Another solution would be to create a new field in
__sk_buff but it's more cumbersome.
I will add a comment.

>
> Looks like somewhat odd 'End.BPF' name comes from similar names in SRv6 draft.
> Do you plan to disclose such End.BPF action in the draft as well?
This is something I've discussed with David Lebrun (the author of the Segment
Routing implementation). There's no plan to disclose an End.BPF action as-is
in the draft, since eBPF is really specific to Linux, and David doesn't mind not
having a 1:1 mapping between the actions of the draft and the implemented
ones. Writing "End.BPF" instead of just "bpf" is important to indicate that the
action will advance to the next segment by itself, like all other End actions.
One could imagine adding later a T.BPF action (a transit action), whose SID
wouldn't have to be a segment, but that could still e.g. add/edit/delete TLVs.

>
> Thanks
>

^ permalink raw reply	[flat|nested] 12+ messages in thread
* Re: [PATCH net-next RFC 0/5] ipv6: sr: introduce seg6local End.BPF action
  2018-04-03 11:16   ` Mathieu Xhonneux
@ 2018-04-03 13:40     ` David Lebrun
  2018-04-03 14:25       ` David Lebrun
  0 siblings, 1 reply; 12+ messages in thread
From: David Lebrun @ 2018-04-03 13:40 UTC (permalink / raw)
  To: Mathieu Xhonneux, Alexei Starovoitov
  Cc: netdev, David Lebrun, Daniel Borkmann

On 04/03/2018 12:16 PM, Mathieu Xhonneux wrote:
> 
>> In patch 2 I was a bit concerned that:
>> +       struct seg6_bpf_srh_state *srh_state = (struct seg6_bpf_srh_state *)
>> +                                              &skb->cb;
>> would not collide with other users of skb->cb, but it seems the way
>> the hook is placed such usage should always be valid.
>> Would be good to add a comment describing the situation.
> Yes, it's indeed a little hack, but this should be OK since the IPv6 layer does
> not use the cb field. Another solution would be to create a new field in
> __sk_buff but it's more cumbersome.
> I will add a comment.

Good point. The IPv6 layer *does* use the cb field through the IP6CB() 
macro. It is first filled in ipv6_rcv() for ingress packets and used, 
among others, in the input path by extension headers processing 
functions to store EH offsets.

Given that input_action_end_bpf is called in the forwarding path 	 and 
terminates with a call to dst_input(), IP6CB() will be then reset by 
ipv6_rcv(), and the use of skb->cb here indeed should not collide with 
other users.

> 
>> Looks like somewhat odd 'End.BPF' name comes from similar names in SRv6 draft.
>> Do you plan to disclose such End.BPF action in the draft as well?
> This is something I've discussed with David Lebrun (the author of the Segment
> Routing implementation). There's no plan to disclose an End.BPF action as-is
> in the draft, since eBPF is really specific to Linux, and David doesn't mind not
> having a 1:1 mapping between the actions of the draft and the implemented
> ones. Writing "End.BPF" instead of just "bpf" is important to indicate that the
> action will advance to the next segment by itself, like all other End actions.
> One could imagine adding later a T.BPF action (a transit action), whose SID
> wouldn't have to be a segment, but that could still e.g. add/edit/delete TLVs.
> 

To clarify, I don't see why we shouldn't support "experimental" features 
that are not defined in draft-6man-segment-routing-header. However, we 
could create a separate draft describing the End.BPF feature, but that's 
perhaps best left for after the ongoing draft's last call.

David

^ permalink raw reply	[flat|nested] 12+ messages in thread
* Re: [PATCH net-next RFC 0/5] ipv6: sr: introduce seg6local End.BPF action
  2018-04-03 13:40     ` David Lebrun
@ 2018-04-03 14:25       ` David Lebrun
  2018-04-03 14:51         ` Eric Dumazet
  2018-04-04  9:34         ` Mathieu Xhonneux
  0 siblings, 2 replies; 12+ messages in thread
From: David Lebrun @ 2018-04-03 14:25 UTC (permalink / raw)
  To: Mathieu Xhonneux, Alexei Starovoitov
  Cc: netdev, David Lebrun, Daniel Borkmann

On 04/03/2018 02:40 PM, David Lebrun wrote:
> On 04/03/2018 12:16 PM, Mathieu Xhonneux wrote:
>>
>>> In patch 2 I was a bit concerned that:
>>> +       struct seg6_bpf_srh_state *srh_state = (struct 
>>> seg6_bpf_srh_state *)
>>> +                                              &skb->cb;
>>> would not collide with other users of skb->cb, but it seems the way
>>> the hook is placed such usage should always be valid.
>>> Would be good to add a comment describing the situation.
>> Yes, it's indeed a little hack, but this should be OK since the IPv6 
>> layer does
>> not use the cb field. Another solution would be to create a new field in
>> __sk_buff but it's more cumbersome.
>> I will add a comment.
> 
> Good point. The IPv6 layer *does* use the cb field through the IP6CB() 
> macro. It is first filled in ipv6_rcv() for ingress packets and used, 
> among others, in the input path by extension headers processing 
> functions to store EH offsets.
> 
> Given that input_action_end_bpf is called in the forwarding path      
> and terminates with a call to dst_input(), IP6CB() will be then reset by 
> ipv6_rcv(), and the use of skb->cb here indeed should not collide with 
> other users.

Actually I'm wrong here. dst_input() will call either ip6_input() or 
ip6_forward(), not ipv6_rcv(). Both functions expect IP6CB() to be set,
so using skb->cb here will interfere with them.

What about saving and restoring the IPv6 CB, similarly to what TCP does 
with tcp_v6_restore_cb() ?

David

^ permalink raw reply	[flat|nested] 12+ messages in thread
* Re: [PATCH net-next RFC 0/5] ipv6: sr: introduce seg6local End.BPF action
  2018-04-03 14:25       ` David Lebrun
@ 2018-04-03 14:51         ` Eric Dumazet
  2018-04-04  9:34         ` Mathieu Xhonneux
  1 sibling, 0 replies; 12+ messages in thread
From: Eric Dumazet @ 2018-04-03 14:51 UTC (permalink / raw)
  To: David Lebrun, Mathieu Xhonneux, Alexei Starovoitov
  Cc: netdev, David Lebrun, Daniel Borkmann



On 04/03/2018 07:25 AM, David Lebrun wrote:
> 
> What about saving and restoring the IPv6 CB, similarly to what TCP does with tcp_v6_restore_cb() ?

Note that TCP only moves IPCB around in skb->cb[] for cache locality gains.

Now we switched to rb-tree for out-of-order queue, these gains might be marginal.

^ permalink raw reply	[flat|nested] 12+ messages in thread
* Re: [PATCH net-next RFC 0/5] ipv6: sr: introduce seg6local End.BPF action
  2018-04-03 14:25       ` David Lebrun
  2018-04-03 14:51         ` Eric Dumazet
@ 2018-04-04  9:34         ` Mathieu Xhonneux
  1 sibling, 0 replies; 12+ messages in thread
From: Mathieu Xhonneux @ 2018-04-04  9:34 UTC (permalink / raw)
  To: David Lebrun; +Cc: Alexei Starovoitov, netdev, David Lebrun, Daniel Borkmann

2018-04-03 16:25 GMT+02:00 David Lebrun <dav.lebrun@gmail.com>:
> Actually I'm wrong here. dst_input() will call either ip6_input() or
> ip6_forward(), not ipv6_rcv(). Both functions expect IP6CB() to be set,
> so using skb->cb here will interfere with them.
>
> What about saving and restoring the IPv6 CB, similarly to what TCP does with
> tcp_v6_restore_cb() ?


Yes. I can change the call to bpf_prog_run_save_cb to bpf_prog_run_clear_cb,
and then manually save/restore the IPv6 CB in input_action_end_bpf.

Or is there maybe a better solution to share some state between the bpf caller
and helpers, that does not need access to skb->cb ?

^ permalink raw reply	[flat|nested] 12+ messages in thread
end of thread, other threads:[~2018-04-04  9:34 UTC | newest]

Thread overview: 12+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-03-23 10:15 [PATCH net-next RFC 0/5] ipv6: sr: introduce seg6local End.BPF action Mathieu Xhonneux
2018-03-23 10:16 ` [PATCH net-next RFC 1/5] ipv6: sr: export function lookup_nexthop Mathieu Xhonneux
2018-03-23 10:16 ` [PATCH next-next RFC 2/5] bpf: Add IPv6 Segment Routing helpers Mathieu Xhonneux
2018-03-23 10:16 ` [PATCH net-next RFC 3/5] bpf: Split lwt inout verifier structures Mathieu Xhonneux
2018-03-23 10:16 ` [PATCH net-next RFC 4/5] ipv6: sr: Add seg6local action End.BPF Mathieu Xhonneux
2018-03-23 10:16 ` [PATCH net-next RFC 5/5] selftests/bpf: test for seg6local End.BPF action Mathieu Xhonneux
2018-03-30 23:03 ` [PATCH net-next RFC 0/5] ipv6: sr: introduce " Alexei Starovoitov
2018-04-03 11:16   ` Mathieu Xhonneux
2018-04-03 13:40     ` David Lebrun
2018-04-03 14:25       ` David Lebrun
2018-04-03 14:51         ` Eric Dumazet
2018-04-04  9:34         ` Mathieu Xhonneux

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