ip6_gre: process toobig in a better way

Now ip6gre processes toobig icmp packet by setting gre dev's mtu in
ip6gre_err, which would cause few things not good:

  - It couldn't set mtu with dev_set_mtu due to it's not in user context,
    which causes route cache and idev->cnf.mtu6 not to be updated.

  - It has to update sk dst pmtu in tx path according to gredev->mtu for
    ip6gre, while it updates pmtu again according to lower dst pmtu in
    ip6_tnl_xmit.

  - To change dev->mtu by toobig icmp packet is not a good idea, it should
    only work on pmtu.

This patch is to process toobig by updating the lower dst's pmtu, as later
sk dst pmtu will be updated in ip6_tnl_xmit, the same way as in ip4gre.

Note that gre dev's mtu will not be updated any more, it doesn't make any
sense to change dev's mtu after receiving a toobig packet.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 0684d0ccaaa5e4309eac695ece2ab10e53b4db83..b90bad7a4e56ee59033fae506eceffd6ae50a88f 100644 (file)
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -403,9 +403,8 @@ static void ip6gre_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
                return;
 
        switch (type) {
-               __u32 teli;
                struct ipv6_tlv_tnl_enc_lim *tel;
-               __u32 mtu;
+               __u32 teli;
        case ICMPV6_DEST_UNREACH:
                net_dbg_ratelimited("%s: Path to destination invalid or inactive!\n",
                                    t->parms.name);
@@ -436,12 +435,7 @@ static void ip6gre_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
                }
                return;
        case ICMPV6_PKT_TOOBIG:
-               mtu = be32_to_cpu(info) - offset - t->tun_hlen;
-               if (t->dev->type == ARPHRD_ETHER)
-                       mtu -= ETH_HLEN;
-               if (mtu < IPV6_MIN_MTU)
-                       mtu = IPV6_MIN_MTU;
-               t->dev->mtu = mtu;
+               ip6_update_pmtu(skb, net, info, 0, 0, sock_net_uid(net, NULL));
                return;
        case NDISC_REDIRECT:
                ip6_redirect(skb, net, skb->dev->ifindex, 0,
@@ -508,7 +502,6 @@ static netdev_tx_t __gre6_xmit(struct sk_buff *skb,
                               __u32 *pmtu, __be16 proto)
 {
        struct ip6_tnl *tunnel = netdev_priv(dev);
-       struct dst_entry *dst = skb_dst(skb);
        __be16 protocol;
 
        if (dev->type == ARPHRD_ETHER)
@@ -527,10 +520,6 @@ static netdev_tx_t __gre6_xmit(struct sk_buff *skb,
        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);
 }