From: Jesper Dangaard Brouer <brouer@redhat.com>
To: bpf@vger.kernel.org
Cc: Jesper Dangaard Brouer <brouer@redhat.com>,
netdev@vger.kernel.org, Daniel Borkmann <borkmann@iogearbox.net>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
maze@google.com, lmb@cloudflare.com, shaun@tigera.io,
Lorenzo Bianconi <lorenzo@kernel.org>,
marek@cloudflare.com, John Fastabend <john.fastabend@gmail.com>,
Jakub Kicinski <kuba@kernel.org>,
eyal.birger@gmail.com, colrack@gmail.com
Subject: [PATCH bpf-next V12 3/7] bpf: bpf_fib_lookup return MTU value as output when looked up
Date: Mon, 18 Jan 2021 17:54:25 +0100 [thread overview]
Message-ID: <161098886506.108067.9992602829687634530.stgit@firesoul> (raw)
In-Reply-To: <161098881526.108067.7603213364270807261.stgit@firesoul>
The BPF-helpers for FIB lookup (bpf_xdp_fib_lookup and bpf_skb_fib_lookup)
can perform MTU check and return BPF_FIB_LKUP_RET_FRAG_NEEDED. The BPF-prog
don't know the MTU value that caused this rejection.
If the BPF-prog wants to implement PMTU (Path MTU Discovery) (rfc1191) it
need to know this MTU value for the ICMP packet.
Patch change lookup and result struct bpf_fib_lookup, to contain this MTU
value as output via a union with 'tot_len' as this is the value used for
the MTU lookup.
V5:
- Fixed uninit value spotted by Dan Carpenter.
- Name struct output member mtu_result
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
include/uapi/linux/bpf.h | 11 +++++++++--
net/core/filter.c | 22 +++++++++++++++-------
tools/include/uapi/linux/bpf.h | 11 +++++++++--
3 files changed, 33 insertions(+), 11 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c001766adcbc..05bfc8c843dc 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2231,6 +2231,9 @@ union bpf_attr {
* * > 0 one of **BPF_FIB_LKUP_RET_** codes explaining why the
* packet is not forwarded or needs assist from full stack
*
+ * If lookup fails with BPF_FIB_LKUP_RET_FRAG_NEEDED, then the MTU
+ * was exceeded and output params->mtu_result contains the MTU.
+ *
* long bpf_sock_hash_update(struct bpf_sock_ops *skops, struct bpf_map *map, void *key, u64 flags)
* Description
* Add an entry to, or update a sockhash *map* referencing sockets.
@@ -4981,9 +4984,13 @@ struct bpf_fib_lookup {
__be16 sport;
__be16 dport;
- /* total length of packet from network header - used for MTU check */
- __u16 tot_len;
+ union { /* used for MTU check */
+ /* input to lookup */
+ __u16 tot_len; /* L3 length from network hdr (iph->tot_len) */
+ /* output: MTU value */
+ __u16 mtu_result;
+ };
/* input: L3 device index for lookup
* output: device index from FIB lookup
*/
diff --git a/net/core/filter.c b/net/core/filter.c
index d5e6f395cf64..da162e64578a 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5289,12 +5289,14 @@ static const struct bpf_func_proto bpf_skb_get_xfrm_state_proto = {
#if IS_ENABLED(CONFIG_INET) || IS_ENABLED(CONFIG_IPV6)
static int bpf_fib_set_fwd_params(struct bpf_fib_lookup *params,
const struct neighbour *neigh,
- const struct net_device *dev)
+ const struct net_device *dev, u32 mtu)
{
memcpy(params->dmac, neigh->ha, ETH_ALEN);
memcpy(params->smac, dev->dev_addr, ETH_ALEN);
params->h_vlan_TCI = 0;
params->h_vlan_proto = 0;
+ if (mtu)
+ params->mtu_result = mtu; /* union with tot_len */
return 0;
}
@@ -5310,8 +5312,8 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
struct net_device *dev;
struct fib_result res;
struct flowi4 fl4;
+ u32 mtu = 0;
int err;
- u32 mtu;
dev = dev_get_by_index_rcu(net, params->ifindex);
if (unlikely(!dev))
@@ -5378,8 +5380,10 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
if (check_mtu) {
mtu = ip_mtu_from_fib_result(&res, params->ipv4_dst);
- if (params->tot_len > mtu)
+ if (params->tot_len > mtu) {
+ params->mtu_result = mtu; /* union with tot_len */
return BPF_FIB_LKUP_RET_FRAG_NEEDED;
+ }
}
nhc = res.nhc;
@@ -5413,7 +5417,7 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
if (!neigh)
return BPF_FIB_LKUP_RET_NO_NEIGH;
- return bpf_fib_set_fwd_params(params, neigh, dev);
+ return bpf_fib_set_fwd_params(params, neigh, dev, mtu);
}
#endif
@@ -5430,7 +5434,7 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
struct flowi6 fl6;
int strict = 0;
int oif, err;
- u32 mtu;
+ u32 mtu = 0;
/* link local addresses are never forwarded */
if (rt6_need_strict(dst) || rt6_need_strict(src))
@@ -5505,8 +5509,10 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
if (check_mtu) {
mtu = ipv6_stub->ip6_mtu_from_fib6(&res, dst, src);
- if (params->tot_len > mtu)
+ if (params->tot_len > mtu) {
+ params->mtu_result = mtu; /* union with tot_len */
return BPF_FIB_LKUP_RET_FRAG_NEEDED;
+ }
}
if (res.nh->fib_nh_lws)
@@ -5526,7 +5532,7 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
if (!neigh)
return BPF_FIB_LKUP_RET_NO_NEIGH;
- return bpf_fib_set_fwd_params(params, neigh, dev);
+ return bpf_fib_set_fwd_params(params, neigh, dev, mtu);
}
#endif
@@ -5602,6 +5608,8 @@ BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb,
dev = dev_get_by_index_rcu(net, params->ifindex);
if (!is_skb_forwardable(dev, skb))
rc = BPF_FIB_LKUP_RET_FRAG_NEEDED;
+
+ params->mtu_result = dev->mtu; /* union with tot_len */
}
return rc;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index c001766adcbc..05bfc8c843dc 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -2231,6 +2231,9 @@ union bpf_attr {
* * > 0 one of **BPF_FIB_LKUP_RET_** codes explaining why the
* packet is not forwarded or needs assist from full stack
*
+ * If lookup fails with BPF_FIB_LKUP_RET_FRAG_NEEDED, then the MTU
+ * was exceeded and output params->mtu_result contains the MTU.
+ *
* long bpf_sock_hash_update(struct bpf_sock_ops *skops, struct bpf_map *map, void *key, u64 flags)
* Description
* Add an entry to, or update a sockhash *map* referencing sockets.
@@ -4981,9 +4984,13 @@ struct bpf_fib_lookup {
__be16 sport;
__be16 dport;
- /* total length of packet from network header - used for MTU check */
- __u16 tot_len;
+ union { /* used for MTU check */
+ /* input to lookup */
+ __u16 tot_len; /* L3 length from network hdr (iph->tot_len) */
+ /* output: MTU value */
+ __u16 mtu_result;
+ };
/* input: L3 device index for lookup
* output: device index from FIB lookup
*/
next prev parent reply other threads:[~2021-01-18 16:57 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-18 16:54 [PATCH bpf-next V12 0/7] bpf: New approach for BPF MTU handling Jesper Dangaard Brouer
2021-01-18 16:54 ` [PATCH bpf-next V12 1/7] bpf: Remove MTU check in __bpf_skb_max_len Jesper Dangaard Brouer
2021-01-18 16:54 ` [PATCH bpf-next V12 2/7] bpf: fix bpf_fib_lookup helper MTU check for SKB ctx Jesper Dangaard Brouer
2021-01-23 1:47 ` Daniel Borkmann
2021-01-25 15:58 ` Jesper Dangaard Brouer
2021-01-18 16:54 ` Jesper Dangaard Brouer [this message]
2021-01-18 16:54 ` [PATCH bpf-next V12 4/7] bpf: add BPF-helper for MTU checking Jesper Dangaard Brouer
2021-01-23 1:35 ` Daniel Borkmann
2021-01-25 8:41 ` Jesper Dangaard Brouer
2021-01-25 22:27 ` Daniel Borkmann
2021-01-26 9:13 ` Jesper Dangaard Brouer
2021-01-18 16:54 ` [PATCH bpf-next V12 5/7] bpf: drop MTU check when doing TC-BPF redirect to ingress Jesper Dangaard Brouer
2021-01-18 16:54 ` [PATCH bpf-next V12 6/7] selftests/bpf: use bpf_check_mtu in selftest test_cls_redirect Jesper Dangaard Brouer
2021-01-18 16:54 ` [PATCH bpf-next V12 7/7] bpf/selftests: tests using bpf_check_mtu BPF-helper Jesper Dangaard Brouer
2021-01-23 1:49 ` Daniel Borkmann
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