From 8ef9ba4d666614497a057d09b0a6eafc1e34eadf Mon Sep 17 00:00:00 2001
From: Oliver Herms <oliver.peter.herms@gmail.com>
Date: Tue, 3 Nov 2020 11:41:33 +0100
Subject: [PATCH] IPv6: Set SIT tunnel hard_header_len to zero
Due to the legacy usage of hard_header_len for SIT tunnels while
already using infrastructure from net/ipv4/ip_tunnel.c the
calculation of the path MTU in tnl_update_pmtu is incorrect.
This leads to unnecessary creation of MTU exceptions for any
flow going over a SIT tunnel.
As SIT tunnels do not have a header themsevles other than their
transport (L3, L2) headers we're leaving hard_header_len set to zero
as tnl_update_pmtu is already taking care of the transport headers
sizes.
This will also help avoiding unnecessary IPv6 GC runs and spinlock
contention seen when using SIT tunnels and for more than
net.ipv6.route.gc_thresh flows.
Fixes: c54419321455 ("GRE: Refactor GRE tunneling code.")
Signed-off-by: Oliver Herms <oliver.peter.herms@gmail.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20201103104133.GA1573211@tws
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
net/ipv6/sit.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 5e2c34c0ac9736..5e7983cb61546f 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -1128,7 +1128,6 @@ static void ipip6_tunnel_bind_dev(struct net_device *dev)
if (tdev && !netif_is_l3_master(tdev)) {
int t_hlen = tunnel->hlen + sizeof(struct iphdr);
- dev->hard_header_len = tdev->hard_header_len + sizeof(struct iphdr);
dev->mtu = tdev->mtu - t_hlen;
if (dev->mtu < IPV6_MIN_MTU)
dev->mtu = IPV6_MIN_MTU;
@@ -1426,7 +1425,6 @@ static void ipip6_tunnel_setup(struct net_device *dev)
dev->priv_destructor = ipip6_dev_free;
dev->type = ARPHRD_SIT;
- dev->hard_header_len = LL_MAX_HEADER + t_hlen;
dev->mtu = ETH_DATA_LEN - t_hlen;
dev->min_mtu = IPV6_MIN_MTU;
dev->max_mtu = IP6_MAX_MTU - t_hlen;
--
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