In our test lab, we have a simple SCTP client connecting to a SCTP server via an IPVS load balancer. On some machines, load balancing works, but on others the initial handshake just fails, thus no SCTP connection whatsoever can be established! We observed that the SCTP INIT-ACK handshake reply from the IPVS machine to the client had a correct IP checksum, but corrupt SCTP checksum when forwarded, thus on the client-side the packet was dropped and an intial handshake retriggered until all attempts run into the void. To fix this issue, this patch i) adds a missing CHECKSUM_UNNECESSARY after the full checksum (re-)calculation (as done in IPVS TCP and UDP code as well), and ii) calculates the checksum in little-endian format (as fixed with the SCTP code in commit 4458f04c: sctp: Clean up sctp checksumming code). Stable backport of upstream commit 4b47bc9a. Cc: Julian Anastasov <ja@xxxxxx> Cc: Simon Horman <horms@xxxxxxxxxxxx> Cc: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> Signed-off-by: Daniel Borkmann <dborkman@xxxxxxxxxx> --- net/netfilter/ipvs/ip_vs_proto_sctp.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/net/netfilter/ipvs/ip_vs_proto_sctp.c b/net/netfilter/ipvs/ip_vs_proto_sctp.c index 9f3fb75..94bb367 100644 --- a/net/netfilter/ipvs/ip_vs_proto_sctp.c +++ b/net/netfilter/ipvs/ip_vs_proto_sctp.c @@ -70,7 +70,7 @@ sctp_snat_handler(struct sk_buff *skb, sctp_sctphdr_t *sctph; unsigned int sctphoff; struct sk_buff *iter; - __be32 crc32; + __u32 crc32; #ifdef CONFIG_IP_VS_IPV6 if (cp->af == AF_INET6) @@ -101,8 +101,9 @@ sctp_snat_handler(struct sk_buff *skb, skb_walk_frags(skb, iter) crc32 = sctp_update_cksum((u8 *) iter->data, skb_headlen(iter), crc32); - crc32 = sctp_end_cksum(crc32); - sctph->checksum = crc32; + sctph->checksum = sctp_end_cksum(crc32); + + skb->ip_summed = CHECKSUM_UNNECESSARY; return 1; } @@ -114,7 +115,7 @@ sctp_dnat_handler(struct sk_buff *skb, sctp_sctphdr_t *sctph; unsigned int sctphoff; struct sk_buff *iter; - __be32 crc32; + __u32 crc32; #ifdef CONFIG_IP_VS_IPV6 if (cp->af == AF_INET6) @@ -145,8 +146,9 @@ sctp_dnat_handler(struct sk_buff *skb, skb_walk_frags(skb, iter) crc32 = sctp_update_cksum((u8 *) iter->data, skb_headlen(iter), crc32); - crc32 = sctp_end_cksum(crc32); - sctph->checksum = crc32; + sctph->checksum = sctp_end_cksum(crc32); + + skb->ip_summed = CHECKSUM_UNNECESSARY; return 1; } -- 1.7.11.7 -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
