ip6_gre: process toobig in a better way (fe1a4ca0) · Commits · 戴 / test

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>

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);
		}

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