netdev - [PATCH net 3/4] udp: do not transition UDP fraglist to unnecessary checksum

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Date: Fri, 15 Mar 2024 16:17:19 +0100
From: Antoine Tenart <atenart@...nel.org>
To: davem@...emloft.net,
	kuba@...nel.org,
	pabeni@...hat.com,
	edumazet@...gle.com
Cc: Antoine Tenart <atenart@...nel.org>,
	steffen.klassert@...unet.com,
	netdev@...r.kernel.org
Subject: [PATCH net 3/4] udp: do not transition UDP fraglist to unnecessary checksum

udp4/6_gro_complete transition fraglist packets to CHECKSUM_UNNECESSARY
and sets their checksum level based on if the packet is recognized to be
a tunneled one. However there is no safe way to detect a packet is a
tunneled one and in case such packet is GROed at the UDP level, setting
a wrong checksum level will lead to later errors. For example if those
packets are forwarded to the Tx path they could produce the following
dump:

  gen01: hw csum failure
  skb len=3008 headroom=160 headlen=1376 tailroom=0
  mac=(106,14) net=(120,40) trans=160
  shinfo(txflags=0 nr_frags=0 gso(size=0 type=0 segs=0))
  csum(0xffff232e ip_summed=2 complete_sw=0 valid=0 level=0)
  hash(0x77e3d716 sw=1 l4=1) proto=0x86dd pkttype=0 iif=12
  ...

Fixes: 9fd1ff5d2ac7 ("udp: Support UDP fraglist GRO/GSO.")
Signed-off-by: Antoine Tenart <atenart@...nel.org>
---
 net/ipv4/udp_offload.c | 8 --------
 net/ipv6/udp_offload.c | 8 --------
 2 files changed, 16 deletions(-)

diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 3bb69464930b..3263ebcaa3f4 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -722,14 +722,6 @@ INDIRECT_CALLABLE_SCOPE int udp4_gro_complete(struct sk_buff *skb, int nhoff)
 		skb_shinfo(skb)->gso_type |= (SKB_GSO_FRAGLIST|SKB_GSO_UDP_L4);
 		skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
 
-		if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
-			if (skb->csum_level < SKB_MAX_CSUM_LEVEL)
-				skb->csum_level++;
-		} else {
-			skb->ip_summed = CHECKSUM_UNNECESSARY;
-			skb->csum_level = 0;
-		}
-
 		return 0;
 	}
 
diff --git a/net/ipv6/udp_offload.c b/net/ipv6/udp_offload.c
index 312bcaeea96f..9289384cb7d0 100644
--- a/net/ipv6/udp_offload.c
+++ b/net/ipv6/udp_offload.c
@@ -174,14 +174,6 @@ INDIRECT_CALLABLE_SCOPE int udp6_gro_complete(struct sk_buff *skb, int nhoff)
 		skb_shinfo(skb)->gso_type |= (SKB_GSO_FRAGLIST|SKB_GSO_UDP_L4);
 		skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
 
-		if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
-			if (skb->csum_level < SKB_MAX_CSUM_LEVEL)
-				skb->csum_level++;
-		} else {
-			skb->ip_summed = CHECKSUM_UNNECESSARY;
-			skb->csum_level = 0;
-		}
-
 		return 0;
 	}
 
-- 
2.44.0