diff options
author | Daniel Borkmann <daniel@iogearbox.net> | 2016-08-05 00:11:12 +0200 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2016-08-08 13:11:43 -0700 |
commit | 479ffcccefd7b04442b0e949f8779b0612e8c75f (patch) | |
tree | 97d83930ebfdd05296018eec0c6bfe19f93b601b /net | |
parent | a2bfe6bf09a5f38df2bd0b1734f5fdee76f9366f (diff) |
bpf: fix checksum fixups on bpf_skb_store_bytes
bpf_skb_store_bytes() invocations above L2 header need BPF_F_RECOMPUTE_CSUM
flag for updates, so that CHECKSUM_COMPLETE will be fixed up along the way.
Where we ran into an issue with bpf_skb_store_bytes() is when we did a
single-byte update on the IPv6 hoplimit despite using BPF_F_RECOMPUTE_CSUM
flag; simple ping via ICMPv6 triggered a hw csum failure as a result. The
underlying issue has been tracked down to a buffer alignment issue.
Meaning, that csum_partial() computations via skb_postpull_rcsum() and
skb_postpush_rcsum() pair invoked had a wrong result since they operated on
an odd address for the hoplimit, while other computations were done on an
even address. This mix doesn't work as-is with skb_postpull_rcsum(),
skb_postpush_rcsum() pair as it always expects at least half-word alignment
of input buffers, which is normally the case. Thus, instead of these helpers
using csum_sub() and (implicitly) csum_add(), we need to use csum_block_sub(),
csum_block_add(), respectively. For unaligned offsets, they rotate the sum
to align it to a half-word boundary again, otherwise they work the same as
csum_sub() and csum_add().
Adding __skb_postpull_rcsum(), __skb_postpush_rcsum() variants that take the
offset as an input and adapting bpf_skb_store_bytes() to them fixes the hw
csum failures again. The skb_postpull_rcsum(), skb_postpush_rcsum() helpers
use a 0 constant for offset so that the compiler optimizes the offset & 1
test away and generates the same code as with csum_sub()/_add().
Fixes: 608cd71a9c7c ("tc: bpf: generalize pedit action")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r-- | net/core/filter.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index c46244f83a8f..5ecd5c9836c3 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -1401,7 +1401,7 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags) return -EFAULT; if (flags & BPF_F_RECOMPUTE_CSUM) - skb_postpull_rcsum(skb, ptr, len); + __skb_postpull_rcsum(skb, ptr, len, offset); memcpy(ptr, from, len); @@ -1410,7 +1410,7 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags) skb_store_bits(skb, offset, ptr, len); if (flags & BPF_F_RECOMPUTE_CSUM) - skb_postpush_rcsum(skb, ptr, len); + __skb_postpush_rcsum(skb, ptr, len, offset); if (flags & BPF_F_INVALIDATE_HASH) skb_clear_hash(skb); |