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authorFlorian Westphal <fw@strlen.de>2021-01-06 00:15:22 +0100
committerJakub Kicinski <kuba@kernel.org>2021-01-07 14:42:36 -0800
commit50c661670f6a3908c273503dfa206dfc7aa54c07 (patch)
treeb9ab3ccfa4122744ee8c847c774c506329e9729c /net
parent9e7a67dee27902fedab880b9af909bd4acd0fba9 (diff)
net: fix pmtu check in nopmtudisc mode
For some reason ip_tunnel insist on setting the DF bit anyway when the inner header has the DF bit set, EVEN if the tunnel was configured with 'nopmtudisc'. This means that the script added in the previous commit cannot be made to work by adding the 'nopmtudisc' flag to the ip tunnel configuration. Doing so breaks connectivity even for the without-conntrack/netfilter scenario. When nopmtudisc is set, the tunnel will skip the mtu check, so no icmp error is sent to client. Then, because inner header has DF set, the outer header gets added with DF bit set as well. IP stack then sends an error to itself because the packet exceeds the device MTU. Fixes: 23a3647bc4f93 ("ip_tunnels: Use skb-len to PMTU check.") Cc: Stefano Brivio <sbrivio@redhat.com> Signed-off-by: Florian Westphal <fw@strlen.de> Acked-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/ip_tunnel.c11
1 files changed, 5 insertions, 6 deletions
diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index ee65c9225178..64594aa755f0 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -759,8 +759,11 @@ void ip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev,
goto tx_error;
}
- if (tnl_update_pmtu(dev, skb, rt, tnl_params->frag_off, inner_iph,
- 0, 0, false)) {
+ df = tnl_params->frag_off;
+ if (skb->protocol == htons(ETH_P_IP) && !tunnel->ignore_df)
+ df |= (inner_iph->frag_off & htons(IP_DF));
+
+ if (tnl_update_pmtu(dev, skb, rt, df, inner_iph, 0, 0, false)) {
ip_rt_put(rt);
goto tx_error;
}
@@ -788,10 +791,6 @@ void ip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev,
ttl = ip4_dst_hoplimit(&rt->dst);
}
- df = tnl_params->frag_off;
- if (skb->protocol == htons(ETH_P_IP) && !tunnel->ignore_df)
- df |= (inner_iph->frag_off&htons(IP_DF));
-
max_headroom = LL_RESERVED_SPACE(rt->dst.dev) + sizeof(struct iphdr)
+ rt->dst.header_len + ip_encap_hlen(&tunnel->encap);
if (max_headroom > dev->needed_headroom)