[RESEND net v3] net: ip_tunnel: fix mtu calculation
From: Vadim Fedorenko <hidden>
Date: 2021-01-29 22:28:39
dev->hard_header_len for tunnel interface is set only when header_ops
are set too and already contains full overhead of any tunnel encapsulation.
That's why there is not need to use this overhead twice in mtu calc.
Fixes: fdafed459998 ("ip_gre: set dev->hard_header_len and dev->needed_headroom properly")
Reported-by: Slava Bacherikov <redacted>
Signed-off-by: Vadim Fedorenko <redacted>
---
net/ipv4/ip_tunnel.c | 16 +++++++---------
1 file changed, 7 insertions(+), 9 deletions(-)
diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index 64594aa..76a420c 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c@@ -317,7 +317,7 @@ static int ip_tunnel_bind_dev(struct net_device *dev) } dev->needed_headroom = t_hlen + hlen; - mtu -= (dev->hard_header_len + t_hlen); + mtu -= t_hlen; if (mtu < IPV4_MIN_MTU) mtu = IPV4_MIN_MTU;
@@ -347,7 +347,7 @@ static struct ip_tunnel *ip_tunnel_create(struct net *net, nt = netdev_priv(dev); t_hlen = nt->hlen + sizeof(struct iphdr); dev->min_mtu = ETH_MIN_MTU; - dev->max_mtu = IP_MAX_MTU - dev->hard_header_len - t_hlen; + dev->max_mtu = IP_MAX_MTU - t_hlen; ip_tunnel_add(itn, nt); return nt;
@@ -488,11 +488,10 @@ static int tnl_update_pmtu(struct net_device *dev, struct sk_buff *skb, int mtu; tunnel_hlen = md ? tunnel_hlen : tunnel->hlen; - pkt_size = skb->len - tunnel_hlen - dev->hard_header_len; + pkt_size = skb->len - tunnel_hlen; if (df) - mtu = dst_mtu(&rt->dst) - dev->hard_header_len - - sizeof(struct iphdr) - tunnel_hlen; + mtu = dst_mtu(&rt->dst) - (sizeof(struct iphdr) + tunnel_hlen); else mtu = skb_valid_dst(skb) ? dst_mtu(skb_dst(skb)) : dev->mtu;
@@ -972,7 +971,7 @@ int __ip_tunnel_change_mtu(struct net_device *dev, int new_mtu, bool strict) { struct ip_tunnel *tunnel = netdev_priv(dev); int t_hlen = tunnel->hlen + sizeof(struct iphdr); - int max_mtu = IP_MAX_MTU - dev->hard_header_len - t_hlen; + int max_mtu = IP_MAX_MTU - t_hlen; if (new_mtu < ETH_MIN_MTU) return -EINVAL;
@@ -1149,10 +1148,9 @@ int ip_tunnel_newlink(struct net_device *dev, struct nlattr *tb[], mtu = ip_tunnel_bind_dev(dev); if (tb[IFLA_MTU]) { - unsigned int max = IP_MAX_MTU - dev->hard_header_len - nt->hlen; + unsigned int max = IP_MAX_MTU - (nt->hlen + sizeof(struct iphdr)); - mtu = clamp(dev->mtu, (unsigned int)ETH_MIN_MTU, - (unsigned int)(max - sizeof(struct iphdr))); + mtu = clamp(dev->mtu, (unsigned int)ETH_MIN_MTU, max); } err = dev_set_mtu(dev, mtu);
--
1.8.3.1