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authorJiri Bohac <jbohac@suse.cz>2022-01-26 16:00:18 +0100
committerSteffen Klassert <steffen.klassert@secunet.com>2022-01-27 07:34:06 +0100
commita6d95c5a628a09be129f25d5663a7e9db8261f51 (patch)
tree3f6bc5a2ff4abde673736d2d3fd088e6cefb384e /net/xfrm
parente03c3bba351f99ad932e8f06baa9da1afc418e02 (diff)
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/xfrm')
-rw-r--r--net/xfrm/xfrm_state.c14
1 files changed, 2 insertions, 12 deletions
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 1ba6fbfe8cdb..b749935152ba 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -2579,7 +2579,7 @@ void xfrm_state_delete_tunnel(struct xfrm_state *x)
}
EXPORT_SYMBOL(xfrm_state_delete_tunnel);
-u32 __xfrm_state_mtu(struct xfrm_state *x, int mtu)
+u32 xfrm_state_mtu(struct xfrm_state *x, int mtu)
{
const struct xfrm_type *type = READ_ONCE(x->type);
struct crypto_aead *aead;
@@ -2610,17 +2610,7 @@ u32 __xfrm_state_mtu(struct xfrm_state *x, int mtu)
return ((mtu - x->props.header_len - crypto_aead_authsize(aead) -
net_adj) & ~(blksize - 1)) + net_adj - 2;
}
-EXPORT_SYMBOL_GPL(__xfrm_state_mtu);
-
-u32 xfrm_state_mtu(struct xfrm_state *x, int mtu)
-{
- mtu = __xfrm_state_mtu(x, mtu);
-
- if (x->props.family == AF_INET6 && mtu < IPV6_MIN_MTU)
- return IPV6_MIN_MTU;
-
- return mtu;
-}
+EXPORT_SYMBOL_GPL(xfrm_state_mtu);
int __xfrm_init_state(struct xfrm_state *x, bool init_replay, bool offload)
{