ipv6: Handle PMTU in ICMP error handlers.
One tricky issue on the ipv6 side vs. ipv4 is that the ICMP callouts to handle the error pass the 32-bit info cookie in network byte order whereas ipv4 passes it around in host byte order. Like the ipv4 side, we have two helper functions. One for when we have a socket context and one for when we do not. ip6ip6 tunnels are not handled here, because they handle PMTU events by essentially relaying another ICMP packet-too-big message back to the original sender. This patch allows us to get rid of rt6_do_pmtu_disc(). It handles all kinds of situations that simply cannot happen when we do the PMTU update directly using a fully resolved route. In fact, the "plen == 128" check in ip6_rt_update_pmtu() can very likely be removed or changed into a BUG_ON() check. We should never have a prefixed ipv6 route when we get there. Another piece of strange history here is that TCP and DCCP, unlike in ipv4, never invoke the update_pmtu() method from their ICMP error handlers. This is incredibly astonishing since this is the context where we have the most accurate context in which to make a PMTU update, namely we have a fully connected socket and associated cached socket route. Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Родитель
3639339553
Коммит
81aded2467
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@ -140,10 +140,10 @@ extern void rt6_redirect(const struct in6_addr *dest,
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u8 *lladdr,
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int on_link);
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extern void rt6_pmtu_discovery(const struct in6_addr *daddr,
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const struct in6_addr *saddr,
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struct net_device *dev,
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u32 pmtu);
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extern void ip6_update_pmtu(struct sk_buff *skb, struct net *net, __be32 mtu,
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int oif, u32 mark);
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extern void ip6_sk_update_pmtu(struct sk_buff *skb, struct sock *sk,
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__be32 mtu);
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struct netlink_callback;
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@ -165,6 +165,8 @@ static void dccp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
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} else
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dst_hold(dst);
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dst->ops->update_pmtu(dst, ntohl(info));
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if (inet_csk(sk)->icsk_pmtu_cookie > dst_mtu(dst)) {
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dccp_sync_mss(sk, dst_mtu(dst));
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} /* else let the usual retransmit timer handle it */
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@ -35,6 +35,7 @@
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#include <linux/pfkeyv2.h>
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#include <linux/string.h>
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#include <linux/scatterlist.h>
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#include <net/ip6_route.h>
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#include <net/icmp.h>
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#include <net/ipv6.h>
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#include <net/protocol.h>
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@ -621,7 +622,7 @@ static void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
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NETDEBUG(KERN_DEBUG "pmtu discovery on SA AH/%08x/%pI6\n",
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ntohl(ah->spi), &iph->daddr);
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ip6_update_pmtu(skb, net, info, 0, 0);
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xfrm_state_put(x);
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}
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@ -39,6 +39,7 @@
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#include <linux/random.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <net/ip6_route.h>
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#include <net/icmp.h>
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#include <net/ipv6.h>
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#include <net/protocol.h>
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@ -442,6 +443,7 @@ static void esp6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
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return;
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pr_debug("pmtu discovery on SA ESP/%08x/%pI6\n",
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ntohl(esph->spi), &iph->daddr);
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ip6_update_pmtu(skb, net, info, 0, 0);
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xfrm_state_put(x);
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}
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@ -649,7 +649,6 @@ static int icmpv6_rcv(struct sk_buff *skb)
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struct net_device *dev = skb->dev;
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struct inet6_dev *idev = __in6_dev_get(dev);
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const struct in6_addr *saddr, *daddr;
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const struct ipv6hdr *orig_hdr;
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struct icmp6hdr *hdr;
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u8 type;
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@ -661,7 +660,7 @@ static int icmpv6_rcv(struct sk_buff *skb)
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XFRM_STATE_ICMP))
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goto drop_no_count;
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if (!pskb_may_pull(skb, sizeof(*hdr) + sizeof(*orig_hdr)))
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if (!pskb_may_pull(skb, sizeof(*hdr) + sizeof(struct ipv6hdr)))
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goto drop_no_count;
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nh = skb_network_offset(skb);
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@ -722,9 +721,6 @@ static int icmpv6_rcv(struct sk_buff *skb)
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if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
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goto discard_it;
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hdr = icmp6_hdr(skb);
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orig_hdr = (struct ipv6hdr *) (hdr + 1);
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rt6_pmtu_discovery(&orig_hdr->daddr, &orig_hdr->saddr, dev,
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ntohl(hdr->icmp6_mtu));
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/*
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* Drop through to notify
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@ -46,6 +46,7 @@
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#include <linux/list.h>
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#include <linux/vmalloc.h>
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#include <linux/rtnetlink.h>
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#include <net/ip6_route.h>
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#include <net/icmp.h>
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#include <net/ipv6.h>
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#include <net/protocol.h>
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@ -74,6 +75,7 @@ static void ipcomp6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
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pr_debug("pmtu discovery on SA IPCOMP/%08x/%pI6\n",
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spi, &iph->daddr);
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ip6_update_pmtu(skb, net, info, 0, 0);
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xfrm_state_put(x);
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}
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@ -328,9 +328,10 @@ static void rawv6_err(struct sock *sk, struct sk_buff *skb,
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return;
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harderr = icmpv6_err_convert(type, code, &err);
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if (type == ICMPV6_PKT_TOOBIG)
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if (type == ICMPV6_PKT_TOOBIG) {
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ip6_sk_update_pmtu(skb, sk, info);
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harderr = (np->pmtudisc == IPV6_PMTUDISC_DO);
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}
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if (np->recverr) {
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u8 *payload = skb->data;
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if (!inet->hdrincl)
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143
net/ipv6/route.c
143
net/ipv6/route.c
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@ -1049,7 +1049,10 @@ static void ip6_rt_update_pmtu(struct dst_entry *dst, u32 mtu)
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{
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struct rt6_info *rt6 = (struct rt6_info*)dst;
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dst_confirm(dst);
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if (mtu < dst_mtu(dst) && rt6->rt6i_dst.plen == 128) {
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struct net *net = dev_net(dst->dev);
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rt6->rt6i_flags |= RTF_MODIFIED;
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if (mtu < IPV6_MIN_MTU) {
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u32 features = dst_metric(dst, RTAX_FEATURES);
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@ -1058,9 +1061,39 @@ static void ip6_rt_update_pmtu(struct dst_entry *dst, u32 mtu)
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dst_metric_set(dst, RTAX_FEATURES, features);
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}
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dst_metric_set(dst, RTAX_MTU, mtu);
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rt6_update_expires(rt6, net->ipv6.sysctl.ip6_rt_mtu_expires);
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}
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}
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void ip6_update_pmtu(struct sk_buff *skb, struct net *net, u32 mtu,
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int oif, __be32 mark)
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{
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const struct ipv6hdr *iph = (struct ipv6hdr *) skb->data;
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struct dst_entry *dst;
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struct flowi6 fl6;
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memset(&fl6, 0, sizeof(fl6));
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fl6.flowi6_oif = oif;
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fl6.flowi6_mark = mark;
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fl6.flowi6_flags = FLOWI_FLAG_PRECOW_METRICS;
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fl6.daddr = iph->daddr;
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fl6.saddr = iph->saddr;
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fl6.flowlabel = (*(__be32 *) iph) & IPV6_FLOWINFO_MASK;
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dst = ip6_route_output(net, NULL, &fl6);
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if (!dst->error)
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ip6_rt_update_pmtu(dst, ntohl(mtu));
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dst_release(dst);
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}
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EXPORT_SYMBOL_GPL(ip6_update_pmtu);
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void ip6_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, __be32 mtu)
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{
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ip6_update_pmtu(skb, sock_net(sk), mtu,
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sk->sk_bound_dev_if, sk->sk_mark);
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}
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EXPORT_SYMBOL_GPL(ip6_sk_update_pmtu);
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static unsigned int ip6_default_advmss(const struct dst_entry *dst)
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{
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struct net_device *dev = dst->dev;
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@ -1703,116 +1736,6 @@ out:
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dst_release(&rt->dst);
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}
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/*
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* Handle ICMP "packet too big" messages
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* i.e. Path MTU discovery
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*/
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static void rt6_do_pmtu_disc(const struct in6_addr *daddr, const struct in6_addr *saddr,
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struct net *net, u32 pmtu, int ifindex)
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{
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struct rt6_info *rt, *nrt;
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int allfrag = 0;
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again:
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rt = rt6_lookup(net, daddr, saddr, ifindex, 0);
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if (!rt)
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return;
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if (rt6_check_expired(rt)) {
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ip6_del_rt(rt);
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goto again;
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}
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if (pmtu >= dst_mtu(&rt->dst))
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goto out;
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if (pmtu < IPV6_MIN_MTU) {
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/*
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* According to RFC2460, PMTU is set to the IPv6 Minimum Link
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* MTU (1280) and a fragment header should always be included
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* after a node receiving Too Big message reporting PMTU is
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* less than the IPv6 Minimum Link MTU.
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*/
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pmtu = IPV6_MIN_MTU;
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allfrag = 1;
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}
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/* New mtu received -> path was valid.
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They are sent only in response to data packets,
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so that this nexthop apparently is reachable. --ANK
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*/
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dst_confirm(&rt->dst);
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/* Host route. If it is static, it would be better
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not to override it, but add new one, so that
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when cache entry will expire old pmtu
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would return automatically.
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*/
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if (rt->rt6i_flags & RTF_CACHE) {
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dst_metric_set(&rt->dst, RTAX_MTU, pmtu);
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if (allfrag) {
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u32 features = dst_metric(&rt->dst, RTAX_FEATURES);
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features |= RTAX_FEATURE_ALLFRAG;
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dst_metric_set(&rt->dst, RTAX_FEATURES, features);
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}
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rt6_update_expires(rt, net->ipv6.sysctl.ip6_rt_mtu_expires);
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rt->rt6i_flags |= RTF_MODIFIED;
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goto out;
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}
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/* Network route.
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Two cases are possible:
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1. It is connected route. Action: COW
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2. It is gatewayed route or NONEXTHOP route. Action: clone it.
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*/
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if (!dst_get_neighbour_noref_raw(&rt->dst) && !(rt->rt6i_flags & RTF_NONEXTHOP))
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nrt = rt6_alloc_cow(rt, daddr, saddr);
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else
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nrt = rt6_alloc_clone(rt, daddr);
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if (nrt) {
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dst_metric_set(&nrt->dst, RTAX_MTU, pmtu);
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if (allfrag) {
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u32 features = dst_metric(&nrt->dst, RTAX_FEATURES);
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features |= RTAX_FEATURE_ALLFRAG;
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dst_metric_set(&nrt->dst, RTAX_FEATURES, features);
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}
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/* According to RFC 1981, detecting PMTU increase shouldn't be
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* happened within 5 mins, the recommended timer is 10 mins.
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* Here this route expiration time is set to ip6_rt_mtu_expires
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* which is 10 mins. After 10 mins the decreased pmtu is expired
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* and detecting PMTU increase will be automatically happened.
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*/
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rt6_update_expires(nrt, net->ipv6.sysctl.ip6_rt_mtu_expires);
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nrt->rt6i_flags |= RTF_DYNAMIC;
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ip6_ins_rt(nrt);
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}
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out:
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dst_release(&rt->dst);
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}
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void rt6_pmtu_discovery(const struct in6_addr *daddr, const struct in6_addr *saddr,
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struct net_device *dev, u32 pmtu)
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{
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struct net *net = dev_net(dev);
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/*
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* RFC 1981 states that a node "MUST reduce the size of the packets it
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* is sending along the path" that caused the Packet Too Big message.
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* Since it's not possible in the general case to determine which
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* interface was used to send the original packet, we update the MTU
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* on the interface that will be used to send future packets. We also
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* update the MTU on the interface that received the Packet Too Big in
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* case the original packet was forced out that interface with
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* SO_BINDTODEVICE or similar. This is the next best thing to the
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* correct behaviour, which would be to update the MTU on all
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* interfaces.
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*/
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rt6_do_pmtu_disc(daddr, saddr, net, pmtu, 0);
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rt6_do_pmtu_disc(daddr, saddr, net, pmtu, dev->ifindex);
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}
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/*
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* Misc support functions
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*/
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@ -415,6 +415,8 @@ static void tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
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} else
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dst_hold(dst);
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dst->ops->update_pmtu(dst, ntohl(info));
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if (inet_csk(sk)->icsk_pmtu_cookie > dst_mtu(dst)) {
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tcp_sync_mss(sk, dst_mtu(dst));
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tcp_simple_retransmit(sk);
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@ -479,6 +479,9 @@ void __udp6_lib_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
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if (sk == NULL)
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return;
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if (type == ICMPV6_PKT_TOOBIG)
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ip6_sk_update_pmtu(skb, sk, info);
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np = inet6_sk(sk);
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if (!icmpv6_err_convert(type, code, &err) && !np->recverr)
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