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Merge branch 'net-fix-inet_proto_csum_replace_by_diff-for-ipv6'

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Paul Chaignon says:

====================
net: Fix inet_proto_csum_replace_by_diff for IPv6

This patchset fixes a bug that causes skb->csum to hold an incorrect
value when calling inet_proto_csum_replace_by_diff for an IPv6 packet
in CHECKSUM_COMPLETE state. This bug affects BPF helper
bpf_l4_csum_replace and IPv6 ILA in adj-transport mode.

In those cases, inet_proto_csum_replace_by_diff updates the L4 checksum
field after an IPv6 address change. These two changes cancel each other
in terms of checksum, so skb->csum shouldn't be updated.

v2: https://lore.kernel.org/aCz84JU60wd8etiT@mail.gmail.com
====================

Link: https://patch.msgid.link/cover.1748509484.git.paul.chaignon@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski
2025-05-30 19:53:53 -07:00
parent 44abca1fe3 ead7f9b8de
commit 558428921e
6 changed files with 13 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
include/net/checksum.h
View File

@@ -152,7 +152,7 @@ void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb,
const __be32 *from, const __be32 *to,
bool pseudohdr);
void inet_proto_csum_replace_by_diff(__sum16 *sum, struct sk_buff *skb,
__wsum diff, bool pseudohdr);
__wsum diff, bool pseudohdr, bool ipv6);
static __always_inline
void inet_proto_csum_replace2(__sum16 *sum, struct sk_buff *skb,

2
include/uapi/linux/bpf.h
View File

@@ -2056,6 +2056,7 @@ union bpf_attr {
* for updates resulting in a null checksum the value is set to
* **CSUM_MANGLED_0** instead. Flag **BPF_F_PSEUDO_HDR** indicates
* that the modified header field is part of the pseudo-header.
* Flag **BPF_F_IPV6** should be set for IPv6 packets.
*
* This helper works in combination with **bpf_csum_diff**\ (),
* which does not update the checksum in-place, but offers more
@@ -6072,6 +6073,7 @@ enum {
BPF_F_PSEUDO_HDR = (1ULL << 4),
BPF_F_MARK_MANGLED_0 = (1ULL << 5),
BPF_F_MARK_ENFORCE = (1ULL << 6),
BPF_F_IPV6 = (1ULL << 7),
};
/* BPF_FUNC_skb_set_tunnel_key and BPF_FUNC_skb_get_tunnel_key flags. */

5
net/core/filter.c
View File

@@ -1968,10 +1968,11 @@ BPF_CALL_5(bpf_l4_csum_replace, struct sk_buff *, skb, u32, offset,
bool is_pseudo = flags & BPF_F_PSEUDO_HDR;
bool is_mmzero = flags & BPF_F_MARK_MANGLED_0;
bool do_mforce = flags & BPF_F_MARK_ENFORCE;
bool is_ipv6 = flags & BPF_F_IPV6;
__sum16 *ptr;
if (unlikely(flags & ~(BPF_F_MARK_MANGLED_0 | BPF_F_MARK_ENFORCE |
BPF_F_PSEUDO_HDR | BPF_F_HDR_FIELD_MASK)))
BPF_F_PSEUDO_HDR | BPF_F_HDR_FIELD_MASK | BPF_F_IPV6)))
return -EINVAL;
if (unlikely(offset > 0xffff || offset & 1))
return -EFAULT;
@@ -1987,7 +1988,7 @@ BPF_CALL_5(bpf_l4_csum_replace, struct sk_buff *, skb, u32, offset,
if (unlikely(from != 0))
return -EINVAL;
inet_proto_csum_replace_by_diff(ptr, skb, to, is_pseudo);
inet_proto_csum_replace_by_diff(ptr, skb, to, is_pseudo, is_ipv6);
break;
case 2:
inet_proto_csum_replace2(ptr, skb, from, to, is_pseudo);

4
net/core/utils.c
View File

@@ -473,11 +473,11 @@ void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb,
EXPORT_SYMBOL(inet_proto_csum_replace16);
void inet_proto_csum_replace_by_diff(__sum16 *sum, struct sk_buff *skb,
__wsum diff, bool pseudohdr)
__wsum diff, bool pseudohdr, bool ipv6)
{
if (skb->ip_summed != CHECKSUM_PARTIAL) {
csum_replace_by_diff(sum, diff);
if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr)
if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr && !ipv6)
skb->csum = ~csum_sub(diff, skb->csum);
} else if (pseudohdr) {
*sum = ~csum_fold(csum_add(diff, csum_unfold(*sum)));

6
net/ipv6/ila/ila_common.c
View File

@@ -86,7 +86,7 @@ static void ila_csum_adjust_transport(struct sk_buff *skb,
diff = get_csum_diff(ip6h, p);
inet_proto_csum_replace_by_diff(&th->check, skb,
diff, true);
diff, true, true);
}
break;
case NEXTHDR_UDP:
@@ -97,7 +97,7 @@ static void ila_csum_adjust_transport(struct sk_buff *skb,
if (uh->check || skb->ip_summed == CHECKSUM_PARTIAL) {
diff = get_csum_diff(ip6h, p);
inet_proto_csum_replace_by_diff(&uh->check, skb,
diff, true);
diff, true, true);
if (!uh->check)
uh->check = CSUM_MANGLED_0;
}
@@ -111,7 +111,7 @@ static void ila_csum_adjust_transport(struct sk_buff *skb,
diff = get_csum_diff(ip6h, p);
inet_proto_csum_replace_by_diff(&ih->icmp6_cksum, skb,
diff, true);
diff, true, true);
}
break;
}

2
tools/include/uapi/linux/bpf.h
View File

@@ -2056,6 +2056,7 @@ union bpf_attr {
* for updates resulting in a null checksum the value is set to
* **CSUM_MANGLED_0** instead. Flag **BPF_F_PSEUDO_HDR** indicates
* that the modified header field is part of the pseudo-header.
* Flag **BPF_F_IPV6** should be set for IPv6 packets.
*
* This helper works in combination with **bpf_csum_diff**\ (),
* which does not update the checksum in-place, but offers more
@@ -6072,6 +6073,7 @@ enum {
BPF_F_PSEUDO_HDR = (1ULL << 4),
BPF_F_MARK_MANGLED_0 = (1ULL << 5),
BPF_F_MARK_ENFORCE = (1ULL << 6),
BPF_F_IPV6 = (1ULL << 7),
};
/* BPF_FUNC_skb_set_tunnel_key and BPF_FUNC_skb_get_tunnel_key flags. */