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Commit fe1a4ca0 authored by Xin Long's avatar Xin Long Committed by David S. Miller
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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: default avatarXin Long <lucien.xin@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 929fc032

net/ipv6/ip6_gre.c

+2 −13
Original line number Diff line number Diff line
@@ -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);

}