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ip6_gre: process toobig in a better way

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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>
This commit is contained in:
Xin Long 2017-11-11 19:06:50 +08:00 committed by David S. Miller
parent 929fc03275
commit fe1a4ca0a2
1 changed files with 2 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
net/ipv6/ip6_gre.c
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@ -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);
}