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authorJiri Bohac <jbohac@suse.cz>2022-01-26 18:00:18 +0300
committerSteffen Klassert <steffen.klassert@secunet.com>2022-01-27 09:34:06 +0300
commita6d95c5a628a09be129f25d5663a7e9db8261f51 (patch)
tree3f6bc5a2ff4abde673736d2d3fd088e6cefb384e /net/ipv4/esp4.c
parente03c3bba351f99ad932e8f06baa9da1afc418e02 (diff)
downloadlinux-a6d95c5a628a09be129f25d5663a7e9db8261f51.tar.xz
Revert "xfrm: xfrm_state_mtu should return at least 1280 for ipv6"
This reverts commit b515d2637276a3810d6595e10ab02c13bfd0b63a. Commit b515d2637276a3810d6595e10ab02c13bfd0b63a ("xfrm: xfrm_state_mtu should return at least 1280 for ipv6") in v5.14 breaks the TCP MSS calculation in ipsec transport mode, resulting complete stalls of TCP connections. This happens when the (P)MTU is 1280 or slighly larger. The desired formula for the MSS is: MSS = (MTU - ESP_overhead) - IP header - TCP header However, the above commit clamps the (MTU - ESP_overhead) to a minimum of 1280, turning the formula into MSS = max(MTU - ESP overhead, 1280) - IP header - TCP header With the (P)MTU near 1280, the calculated MSS is too large and the resulting TCP packets never make it to the destination because they are over the actual PMTU. The above commit also causes suboptimal double fragmentation in xfrm tunnel mode, as described in https://lore.kernel.org/netdev/20210429202529.codhwpc7w6kbudug@dwarf.suse.cz/ The original problem the above commit was trying to fix is now fixed by commit 6596a0229541270fb8d38d989f91b78838e5e9da ("xfrm: fix MTU regression"). Signed-off-by: Jiri Bohac <jbohac@suse.cz> Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Diffstat (limited to 'net/ipv4/esp4.c')
-rw-r--r--net/ipv4/esp4.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index 851f542928a3..e1b1d080e908 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -671,7 +671,7 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
struct xfrm_dst *dst = (struct xfrm_dst *)skb_dst(skb);
u32 padto;
- padto = min(x->tfcpad, __xfrm_state_mtu(x, dst->child_mtu_cached));
+ padto = min(x->tfcpad, xfrm_state_mtu(x, dst->child_mtu_cached));
if (skb->len < padto)
esp.tfclen = padto - skb->len;
}