[PATCH 3.14 42/59] ipv6: update skb->csum when CE mark is propagated

Greg Kroah-Hartman
2016-01-27T19:22:32Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 34ae6a1aa0540f0f781dd265366036355fdc8930 ]

When a tunnel decapsulates the outer header, it has to comply
with RFC 6080 and eventually propagate CE mark into inner header.

It turns out IP6_ECN_set_ce() does not correctly update skb->csum
for CHECKSUM_COMPLETE packets, triggering infamous "hw csum failure"
messages and stack traces.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/inet_ecn.h | 19 ++++++++++++++++---
net/ipv6/xfrm6_mode_tunnel.c | 2 +-
2 files changed, 17 insertions(+), 4 deletions(-)

--- a/include/net/inet_ecn.h
+++ b/include/net/inet_ecn.h
@@ -111,11 +111,24 @@ static inline void ipv4_copy_dscp(unsign

struct ipv6hdr;

-static inline int IP6_ECN_set_ce(struct ipv6hdr *iph)
+/* Note:
+ * IP_ECN_set_ce() has to tweak IPV4 checksum when setting CE,
+ * meaning both changes have no effect on skb->csum if/when CHECKSUM_COMPLETE
+ * In IPv6 case, no checksum compensates the change in IPv6 header,
+ * so we have to update skb->csum.
+ */
+static inline int IP6_ECN_set_ce(struct sk_buff *skb, struct ipv6hdr *iph)
{
+ __be32 from, to;
+
if (INET_ECN_is_not_ect(ipv6_get_dsfield(iph)))
return 0;
- *(__be32*)iph |= htonl(INET_ECN_CE << 20);
+
+ from = *(__be32 *)iph;
+ to = from | htonl(INET_ECN_CE << 20);
+ *(__be32 *)iph = to;
+ if (skb->ip_summed == CHECKSUM_COMPLETE)
+ skb->csum = csum_add(csum_sub(skb->csum, from), to);
return 1;
}

@@ -142,7 +155,7 @@ static inline int INET_ECN_set_ce(struct
case cpu_to_be16(ETH_P_IPV6):
if (skb_network_header(skb) + sizeof(struct ipv6hdr) <=
skb_tail_pointer(skb))
- return IP6_ECN_set_ce(ipv6_hdr(skb));
+ return IP6_ECN_set_ce(skb, ipv6_hdr(skb));
break;
}

--- a/net/ipv6/xfrm6_mode_tunnel.c
+++ b/net/ipv6/xfrm6_mode_tunnel.c
@@ -83,7 +83,7 @@ static inline void ipip6_ecn_decapsulate
struct ipv6hdr *inner_iph = ipipv6_hdr(skb);

if (INET_ECN_is_ce(ipv6_get_dsfield(outer_iph)))
- IP6_ECN_set_ce(inner_iph);
+ IP6_ECN_set_ce(skb, inner_iph);
}

/* Add encapsulation header.