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From: Ismael Luceno <iluceno@suse.de>
To: linux-kernel@vger.kernel.org
Cc: Ismael Luceno <iluceno@suse.de>,
	Firo Yang <firo.yang@suse.com>,
	Andreas Taschner <andreas.taschner@suse.com>,
	=?UTF-8?q?Michal=20Kube=C4=8Dek?= <mkubecek@suse.com>,
	Simon Horman <horms@verge.net.au>,
	Julian Anastasov <ja@ssi.bg>,
	lvs-devel@vger.kernel.org,
	netfilter-devel@vger.kernel.org,
	netdev@vger.kernel.org,
	coreteam@netfilter.org
Subject: [PATCH] ipvs: Fix checksumming on GSO of SCTP packets
Date: Thu, 18 Apr 2024 16:44:33 +0200
Message-ID: <20240418144434.16407-1-iluceno@suse.de>
Precedence: bulk
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It was observed in the wild that pairs of consecutive packets would leave
the IPVS with the same wrong checksum, and the issue only went away when
disabling GSO.

IPVS needs to avoid computing the SCTP checksum when using GSO.

Co-developed-by: Firo Yang <firo.yang@suse.com>
Signed-off-by: Ismael Luceno <iluceno@suse.de>
Tested-by: Andreas Taschner <andreas.taschner@suse.com>
CC: Michal Kubeček <mkubecek@suse.com>
CC: Simon Horman <horms@verge.net.au>
CC: Julian Anastasov <ja@ssi.bg>
CC: lvs-devel@vger.kernel.org
CC: netfilter-devel@vger.kernel.org
CC: netdev@vger.kernel.org
CC: coreteam@netfilter.org
---
 net/netfilter/ipvs/ip_vs_proto_sctp.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_proto_sctp.c b/net/netfilter/ipvs/ip_vs_proto_sctp.c
index a0921adc31a9..3205b45ce161 100644
--- a/net/netfilter/ipvs/ip_vs_proto_sctp.c
+++ b/net/netfilter/ipvs/ip_vs_proto_sctp.c
@@ -126,7 +126,8 @@ sctp_snat_handler(struct sk_buff *skb, struct ip_vs_protocol *pp,
 	if (sctph->source != cp->vport || payload_csum ||
 	    skb->ip_summed == CHECKSUM_PARTIAL) {
 		sctph->source = cp->vport;
-		sctp_nat_csum(skb, sctph, sctphoff);
+		if (!skb_is_gso_sctp(skb))
+			sctp_nat_csum(skb, sctph, sctphoff);
 	} else {
 		skb->ip_summed = CHECKSUM_UNNECESSARY;
 	}
@@ -174,7 +175,8 @@ sctp_dnat_handler(struct sk_buff *skb, struct ip_vs_protocol *pp,
 	    (skb->ip_summed == CHECKSUM_PARTIAL &&
 	     !(skb_dst(skb)->dev->features & NETIF_F_SCTP_CRC))) {
 		sctph->dest = cp->dport;
-		sctp_nat_csum(skb, sctph, sctphoff);
+		if (!skb_is_gso_sctp(skb))
+			sctp_nat_csum(skb, sctph, sctphoff);
 	} else if (skb->ip_summed != CHECKSUM_PARTIAL) {
 		skb->ip_summed = CHECKSUM_UNNECESSARY;
 	}
-- 
2.43.0