From: Oliver Herms oliver.peter.herms@gmail.com
[ Upstream commit 8ef9ba4d666614497a057d09b0a6eafc1e34eadf ]
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv6/sit.c | 2 -- 1 file changed, 2 deletions(-)
--- a/net/ipv6/sit.c +++ b/net/ipv6/sit.c @@ -1072,7 +1072,6 @@ static void ipip6_tunnel_bind_dev(struct 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; @@ -1372,7 +1371,6 @@ static void ipip6_tunnel_setup(struct ne dev->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->flags = IFF_NOARP; netif_keep_dst(dev);