* [PATCH net-next] bpf: add skb_postpush_rcsum and fix dev_forward_skb occasions
@ 2016-01-07 1:01 Daniel Borkmann
2016-01-07 1:53 ` Hannes Frederic Sowa
2016-01-07 3:22 ` kbuild test robot
0 siblings, 2 replies; 5+ messages in thread
From: Daniel Borkmann @ 2016-01-07 1:01 UTC (permalink / raw)
To: davem; +Cc: alexei.starovoitov, netdev, Daniel Borkmann
Add a small helper skb_postpush_rcsum() and fix up redirect locations
that need CHECKSUM_COMPLETE fixups on ingress. dev_forward_skb() expects
a proper csum that covers also Ethernet header, f.e. since 2c26d34bbcc0
("net/core: Handle csum for CHECKSUM_COMPLETE VXLAN forwarding"), we
also do skb_postpull_rcsum() after pulling Ethernet header off via
eth_type_trans().
When using eBPF in a netns setup f.e. with vxlan in collect metadata mode,
I can trigger the following csum issue with an IPv6 setup:
[ 505.144065] dummy1: hw csum failure
[...]
[ 505.144108] Call Trace:
[ 505.144112] <IRQ> [<ffffffff81372f08>] dump_stack+0x44/0x5c
[ 505.144134] [<ffffffff81607cea>] netdev_rx_csum_fault+0x3a/0x40
[ 505.144142] [<ffffffff815fee3f>] __skb_checksum_complete+0xcf/0xe0
[ 505.144149] [<ffffffff816f0902>] nf_ip6_checksum+0xb2/0x120
[ 505.144161] [<ffffffffa08c0e0e>] icmpv6_error+0x17e/0x328 [nf_conntrack_ipv6]
[ 505.144170] [<ffffffffa0898eca>] ? ip6t_do_table+0x2fa/0x645 [ip6_tables]
[ 505.144177] [<ffffffffa08c0725>] ? ipv6_get_l4proto+0x65/0xd0 [nf_conntrack_ipv6]
[ 505.144189] [<ffffffffa06c9a12>] nf_conntrack_in+0xc2/0x5a0 [nf_conntrack]
[ 505.144196] [<ffffffffa08c039c>] ipv6_conntrack_in+0x1c/0x20 [nf_conntrack_ipv6]
[ 505.144204] [<ffffffff8164385d>] nf_iterate+0x5d/0x70
[ 505.144210] [<ffffffff816438d6>] nf_hook_slow+0x66/0xc0
[ 505.144218] [<ffffffff816bd302>] ipv6_rcv+0x3f2/0x4f0
[ 505.144225] [<ffffffff816bca40>] ? ip6_make_skb+0x1b0/0x1b0
[ 505.144232] [<ffffffff8160b77b>] __netif_receive_skb_core+0x36b/0x9a0
[ 505.144239] [<ffffffff8160bdc8>] ? __netif_receive_skb+0x18/0x60
[ 505.144245] [<ffffffff8160bdc8>] __netif_receive_skb+0x18/0x60
[ 505.144252] [<ffffffff8160ccff>] process_backlog+0x9f/0x140
[ 505.144259] [<ffffffff8160c4a5>] net_rx_action+0x145/0x320
[...]
What happens is that on ingress, we push Ethernet header back in, either
from cls_bpf or right before skb_do_redirect(), but without updating csum.
The "hw csum failure" can be fixed by using the new skb_postpush_rcsum()
helper for the dev_forward_skb() case to correct the csum diff again.
Fixes: 3896d655f4d4 ("bpf: introduce bpf_clone_redirect() helper")
Fixes: 27b29f63058d ("bpf: add bpf_redirect() helper")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
( Given -net pull req is already out and nobody seemed to have triggered
this so far, net-next seems just fine imho. )
include/linux/skbuff.h | 7 +++++++
net/core/filter.c | 17 +++++++++++++----
2 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 6b6bd42..f8fad71 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2805,6 +2805,13 @@ static inline void skb_postpull_rcsum(struct sk_buff *skb,
unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len);
+static inline void skb_postpush_rcsum(struct sk_buff *skb,
+ const void *start, unsigned int len)
+{
+ if (skb->ip_summed == CHECKSUM_COMPLETE)
+ skb->csum = csum_add(skb->csum, csum_partial(start, len, 0));
+}
+
/**
* pskb_trim_rcsum - trim received skb and update checksum
* @skb: buffer to trim
diff --git a/net/core/filter.c b/net/core/filter.c
index 35e6fed..c6160ce 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1368,8 +1368,9 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags)
/* skb_store_bits cannot return -EFAULT here */
skb_store_bits(skb, offset, ptr, len);
- if (BPF_RECOMPUTE_CSUM(flags) && skb->ip_summed == CHECKSUM_COMPLETE)
- skb->csum = csum_add(skb->csum, csum_partial(ptr, len, 0));
+ if (BPF_RECOMPUTE_CSUM(flags))
+ skb_postpush_rcsum(skb, ptr, len);
+
return 0;
}
@@ -1525,8 +1526,12 @@ static u64 bpf_clone_redirect(u64 r1, u64 ifindex, u64 flags, u64 r4, u64 r5)
if (unlikely(!skb2))
return -ENOMEM;
- if (BPF_IS_REDIRECT_INGRESS(flags))
+ if (BPF_IS_REDIRECT_INGRESS(flags)) {
+ if (G_TC_AT(skb2->tc_verd) & AT_INGRESS)
+ skb_postpush_rcsum(skb2, skb_mac_header(skb2),
+ skb2->mac_len);
return dev_forward_skb(dev, skb2);
+ }
skb2->dev = dev;
skb_sender_cpu_clear(skb2);
@@ -1569,8 +1574,12 @@ int skb_do_redirect(struct sk_buff *skb)
return -EINVAL;
}
- if (BPF_IS_REDIRECT_INGRESS(ri->flags))
+ if (BPF_IS_REDIRECT_INGRESS(ri->flags)) {
+ if (G_TC_AT(skb->tc_verd) & AT_INGRESS)
+ skb_postpush_rcsum(skb, skb_mac_header(skb),
+ skb->mac_len);
return dev_forward_skb(dev, skb);
+ }
skb->dev = dev;
skb_sender_cpu_clear(skb);
--
1.9.3
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH net-next] bpf: add skb_postpush_rcsum and fix dev_forward_skb occasions
2016-01-07 1:01 [PATCH net-next] bpf: add skb_postpush_rcsum and fix dev_forward_skb occasions Daniel Borkmann
@ 2016-01-07 1:53 ` Hannes Frederic Sowa
2016-01-07 10:02 ` Daniel Borkmann
2016-01-07 3:22 ` kbuild test robot
1 sibling, 1 reply; 5+ messages in thread
From: Hannes Frederic Sowa @ 2016-01-07 1:53 UTC (permalink / raw)
To: Daniel Borkmann, davem; +Cc: alexei.starovoitov, netdev
On 07.01.2016 02:01, Daniel Borkmann wrote:
> +static inline void skb_postpush_rcsum(struct sk_buff *skb,
> + const void *start, unsigned int len)
> +{
> + if (skb->ip_summed == CHECKSUM_COMPLETE)
> + skb->csum = csum_add(skb->csum, csum_partial(start, len, 0));
skb->csum = csum_partial(start, len, skb->csum);
should work without calling carry-add twice, no?
Bye,
Hannes
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH net-next] bpf: add skb_postpush_rcsum and fix dev_forward_skb occasions
2016-01-07 1:53 ` Hannes Frederic Sowa
@ 2016-01-07 10:02 ` Daniel Borkmann
0 siblings, 0 replies; 5+ messages in thread
From: Daniel Borkmann @ 2016-01-07 10:02 UTC (permalink / raw)
To: Hannes Frederic Sowa, davem; +Cc: alexei.starovoitov, netdev
On 01/07/2016 02:53 AM, Hannes Frederic Sowa wrote:
> On 07.01.2016 02:01, Daniel Borkmann wrote:
>> +static inline void skb_postpush_rcsum(struct sk_buff *skb,
>> + const void *start, unsigned int len)
>> +{
>> + if (skb->ip_summed == CHECKSUM_COMPLETE)
>> + skb->csum = csum_add(skb->csum, csum_partial(start, len, 0));
>
> skb->csum = csum_partial(start, len, skb->csum);
>
> should work without calling carry-add twice, no?
Hmm, indeed, seems you're right. Since the csum_partial() only covers
this particular fragment with feeding initial csum as 0, the result
from the do_csum() stays as is for the first part, and the csum_add()
does effectively the same as if we've fed skb->csum already into
csum_partial().
There are btw couple of other places where this generic helper could be
used as well.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH net-next] bpf: add skb_postpush_rcsum and fix dev_forward_skb occasions
2016-01-07 1:01 [PATCH net-next] bpf: add skb_postpush_rcsum and fix dev_forward_skb occasions Daniel Borkmann
2016-01-07 1:53 ` Hannes Frederic Sowa
@ 2016-01-07 3:22 ` kbuild test robot
2016-01-07 9:05 ` Daniel Borkmann
1 sibling, 1 reply; 5+ messages in thread
From: kbuild test robot @ 2016-01-07 3:22 UTC (permalink / raw)
To: Daniel Borkmann
Cc: kbuild-all, davem, alexei.starovoitov, netdev, Daniel Borkmann
[-- Attachment #1: Type: text/plain, Size: 2508 bytes --]
Hi Daniel,
[auto build test ERROR on net-next/master]
url: https://github.com/0day-ci/linux/commits/Daniel-Borkmann/bpf-add-skb_postpush_rcsum-and-fix-dev_forward_skb-occasions/20160107-090423
config: x86_64-lkp (attached as .config)
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64
All errors (new ones prefixed by >>):
In file included from include/net/sch_generic.h:8:0,
from include/linux/filter.h:16,
from include/net/sock.h:64,
from include/net/inet_sock.h:27,
from include/net/ip.h:30,
from net/core/filter.c:34:
net/core/filter.c: In function 'bpf_clone_redirect':
>> net/core/filter.c:1530:19: error: 'struct sk_buff' has no member named 'tc_verd'
if (G_TC_AT(skb2->tc_verd) & AT_INGRESS)
^
include/uapi/linux/pkt_cls.h:11:25: note: in definition of macro '_TC_MAKE32'
#define _TC_MAKE32(x) ((x))
^
include/uapi/linux/pkt_cls.h:54:26: note: in expansion of macro '_TC_GETVALUE'
#define G_TC_AT(x) _TC_GETVALUE(x,S_TC_AT,M_TC_AT)
^
net/core/filter.c:1530:7: note: in expansion of macro 'G_TC_AT'
if (G_TC_AT(skb2->tc_verd) & AT_INGRESS)
^
net/core/filter.c: In function 'skb_do_redirect':
net/core/filter.c:1578:18: error: 'struct sk_buff' has no member named 'tc_verd'
if (G_TC_AT(skb->tc_verd) & AT_INGRESS)
^
include/uapi/linux/pkt_cls.h:11:25: note: in definition of macro '_TC_MAKE32'
#define _TC_MAKE32(x) ((x))
^
include/uapi/linux/pkt_cls.h:54:26: note: in expansion of macro '_TC_GETVALUE'
#define G_TC_AT(x) _TC_GETVALUE(x,S_TC_AT,M_TC_AT)
^
net/core/filter.c:1578:7: note: in expansion of macro 'G_TC_AT'
if (G_TC_AT(skb->tc_verd) & AT_INGRESS)
^
vim +1530 net/core/filter.c
1524
1525 skb2 = skb_clone(skb, GFP_ATOMIC);
1526 if (unlikely(!skb2))
1527 return -ENOMEM;
1528
1529 if (BPF_IS_REDIRECT_INGRESS(flags)) {
> 1530 if (G_TC_AT(skb2->tc_verd) & AT_INGRESS)
1531 skb_postpush_rcsum(skb2, skb_mac_header(skb2),
1532 skb2->mac_len);
1533 return dev_forward_skb(dev, skb2);
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
[-- Attachment #2: .config.gz --]
[-- Type: application/octet-stream, Size: 22219 bytes --]
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH net-next] bpf: add skb_postpush_rcsum and fix dev_forward_skb occasions
2016-01-07 3:22 ` kbuild test robot
@ 2016-01-07 9:05 ` Daniel Borkmann
0 siblings, 0 replies; 5+ messages in thread
From: Daniel Borkmann @ 2016-01-07 9:05 UTC (permalink / raw)
To: kbuild test robot; +Cc: kbuild-all, davem, alexei.starovoitov, netdev
On 01/07/2016 04:22 AM, kbuild test robot wrote:
> Hi Daniel,
>
> [auto build test ERROR on net-next/master]
>
> url: https://github.com/0day-ci/linux/commits/Daniel-Borkmann/bpf-add-skb_postpush_rcsum-and-fix-dev_forward_skb-occasions/20160107-090423
> config: x86_64-lkp (attached as .config)
> reproduce:
> # save the attached .config to linux build tree
> make ARCH=x86_64
>
> All errors (new ones prefixed by >>):
>
> In file included from include/net/sch_generic.h:8:0,
> from include/linux/filter.h:16,
> from include/net/sock.h:64,
> from include/net/inet_sock.h:27,
> from include/net/ip.h:30,
> from net/core/filter.c:34:
> net/core/filter.c: In function 'bpf_clone_redirect':
>>> net/core/filter.c:1530:19: error: 'struct sk_buff' has no member named 'tc_verd'
> if (G_TC_AT(skb2->tc_verd) & AT_INGRESS)
Hmm, right. I'll add an extra helper function then for v2 as we also
have such ifdef/else in other places for accessing tc_verd.
Thanks,
Daniel
^ permalink raw reply [flat|nested] 5+ messages in thread
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2016-01-07 1:01 [PATCH net-next] bpf: add skb_postpush_rcsum and fix dev_forward_skb occasions Daniel Borkmann
2016-01-07 1:53 ` Hannes Frederic Sowa
2016-01-07 10:02 ` Daniel Borkmann
2016-01-07 3:22 ` kbuild test robot
2016-01-07 9:05 ` Daniel Borkmann
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