Commit 5367cdf3 authored by Sabrina Dubroca's avatar Sabrina Dubroca Committed by Greg Kroah-Hartman

ip_tunnel: don't force DF when MTU is locked

[ Upstream commit 16f7eb2b77b55da816c4e207f3f9440a8cafc00a ]

The various types of tunnels running over IPv4 can ask to set the DF
bit to do PMTU discovery. However, PMTU discovery is subject to the
threshold set by the net.ipv4.route.min_pmtu sysctl, and is also
disabled on routes with "mtu lock". In those cases, we shouldn't set
the DF bit.

This patch makes setting the DF bit conditional on the route's MTU
locking state.

This issue seems to be older than git history.
Signed-off-by: default avatarSabrina Dubroca <>
Reviewed-by: default avatarStefano Brivio <>
Signed-off-by: default avatarDavid S. Miller <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent a09bd930
......@@ -80,7 +80,7 @@ void iptunnel_xmit(struct sock *sk, struct rtable *rt, struct sk_buff *skb,
iph->version = 4;
iph->ihl = sizeof(struct iphdr) >> 2;
iph->frag_off = df;
iph->frag_off = ip_mtu_locked(&rt->dst) ? 0 : df;
iph->protocol = proto;
iph->tos = tos;
iph->daddr = dst;
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