4.13-stable review patch. If anyone has any objections, please let me know.
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From: Xin Long lucien.xin@gmail.com
[ Upstream commit 8aec4959d832bae0889a8e2f348973b5e4abffef ]
When receiving a Toobig icmpv6 packet, ip6gre_err would just set tunnel dev's mtu, that's not enough. For skb_dst(skb)'s pmtu may still be using the old value, it has no chance to be updated with tunnel dev's mtu.
Jianlin found this issue by reducing route's mtu while running netperf, the performance went to 0.
ip6ip6 and ip4ip6 tunnel can work well with this, as they lookup the upper dst and update_pmtu it's pmtu or icmpv6_send a Toobig to upper socket after setting tunnel dev's mtu.
We couldn't do that for ip6_gre, as gre's inner packet could be any protocol, it's difficult to handle them (like lookup upper dst) in a good way.
So this patch is to fix it by updating skb_dst(skb)'s pmtu when dev->mtu < skb_dst(skb)'s pmtu in tx path. It's safe to do this update there, as usually dev->mtu <= skb_dst(skb)'s pmtu and no performance regression can be caused by this.
Fixes: c12b395a4664 ("gre: Support GRE over IPv6") Reported-by: Jianlin Shi jishi@redhat.com Signed-off-by: Xin Long lucien.xin@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv6/ip6_gre.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
--- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -503,8 +503,8 @@ static netdev_tx_t __gre6_xmit(struct sk __u32 *pmtu, __be16 proto) { struct ip6_tnl *tunnel = netdev_priv(dev); - __be16 protocol = (dev->type == ARPHRD_ETHER) ? - htons(ETH_P_TEB) : proto; + struct dst_entry *dst = skb_dst(skb); + __be16 protocol;
if (dev->type == ARPHRD_ETHER) IPCB(skb)->flags = 0; @@ -518,9 +518,14 @@ static netdev_tx_t __gre6_xmit(struct sk tunnel->o_seqno++;
/* Push GRE header. */ + protocol = (dev->type == ARPHRD_ETHER) ? htons(ETH_P_TEB) : proto; gre_build_header(skb, tunnel->tun_hlen, tunnel->parms.o_flags, protocol, tunnel->parms.o_key, htonl(tunnel->o_seqno));
+ /* TooBig packet may have updated dst->dev's mtu */ + if (dst && dst_mtu(dst) > dst->dev->mtu) + dst->ops->update_pmtu(dst, NULL, skb, dst->dev->mtu); + return ip6_tnl_xmit(skb, dev, dsfield, fl6, encap_limit, pmtu, NEXTHDR_GRE); }