Commit 81aded24 authored by David S. Miller's avatar David S. Miller
Browse files

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: default avatarDavid S. Miller <davem@davemloft.net>
parent 36393395
......@@ -140,10 +140,10 @@ extern void rt6_redirect(const struct in6_addr *dest,
u8 *lladdr,
int on_link);
extern void rt6_pmtu_discovery(const struct in6_addr *daddr,
const struct in6_addr *saddr,
struct net_device *dev,
u32 pmtu);
extern void ip6_update_pmtu(struct sk_buff *skb, struct net *net, __be32 mtu,
int oif, u32 mark);
extern void ip6_sk_update_pmtu(struct sk_buff *skb, struct sock *sk,
__be32 mtu);
struct netlink_callback;
......
......@@ -165,6 +165,8 @@ static void dccp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
} else
dst_hold(dst);
dst->ops->update_pmtu(dst, ntohl(info));
if (inet_csk(sk)->icsk_pmtu_cookie > dst_mtu(dst)) {
dccp_sync_mss(sk, dst_mtu(dst));
} /* else let the usual retransmit timer handle it */
......
......@@ -35,6 +35,7 @@
#include <linux/pfkeyv2.h>
#include <linux/string.h>
#include <linux/scatterlist.h>
#include <net/ip6_route.h>
#include <net/icmp.h>
#include <net/ipv6.h>
#include <net/protocol.h>
......@@ -621,7 +622,7 @@ static void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
NETDEBUG(KERN_DEBUG "pmtu discovery on SA AH/%08x/%pI6\n",
ntohl(ah->spi), &iph->daddr);
ip6_update_pmtu(skb, net, info, 0, 0);
xfrm_state_put(x);
}
......
......@@ -39,6 +39,7 @@
#include <linux/random.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <net/ip6_route.h>
#include <net/icmp.h>
#include <net/ipv6.h>
#include <net/protocol.h>
......@@ -442,6 +443,7 @@ static void esp6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
return;
pr_debug("pmtu discovery on SA ESP/%08x/%pI6\n",
ntohl(esph->spi), &iph->daddr);
ip6_update_pmtu(skb, net, info, 0, 0);
xfrm_state_put(x);
}
......
......@@ -649,7 +649,6 @@ static int icmpv6_rcv(struct sk_buff *skb)
struct net_device *dev = skb->dev;
struct inet6_dev *idev = __in6_dev_get(dev);
const struct in6_addr *saddr, *daddr;
const struct ipv6hdr *orig_hdr;
struct icmp6hdr *hdr;
u8 type;
......@@ -661,7 +660,7 @@ static int icmpv6_rcv(struct sk_buff *skb)
XFRM_STATE_ICMP))
goto drop_no_count;
if (!pskb_may_pull(skb, sizeof(*hdr) + sizeof(*orig_hdr)))
if (!pskb_may_pull(skb, sizeof(*hdr) + sizeof(struct ipv6hdr)))
goto drop_no_count;
nh = skb_network_offset(skb);
......@@ -722,9 +721,6 @@ static int icmpv6_rcv(struct sk_buff *skb)
if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
goto discard_it;
hdr = icmp6_hdr(skb);
orig_hdr = (struct ipv6hdr *) (hdr + 1);
rt6_pmtu_discovery(&orig_hdr->daddr, &orig_hdr->saddr, dev,
ntohl(hdr->icmp6_mtu));
/*
* Drop through to notify
......
......@@ -46,6 +46,7 @@
#include <linux/list.h>
#include <linux/vmalloc.h>
#include <linux/rtnetlink.h>
#include <net/ip6_route.h>
#include <net/icmp.h>
#include <net/ipv6.h>
#include <net/protocol.h>
......@@ -74,6 +75,7 @@ static void ipcomp6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
pr_debug("pmtu discovery on SA IPCOMP/%08x/%pI6\n",
spi, &iph->daddr);
ip6_update_pmtu(skb, net, info, 0, 0);
xfrm_state_put(x);
}
......
......@@ -328,9 +328,10 @@ static void rawv6_err(struct sock *sk, struct sk_buff *skb,
return;
harderr = icmpv6_err_convert(type, code, &err);
if (type == ICMPV6_PKT_TOOBIG)
if (type == ICMPV6_PKT_TOOBIG) {
ip6_sk_update_pmtu(skb, sk, info);
harderr = (np->pmtudisc == IPV6_PMTUDISC_DO);
}
if (np->recverr) {
u8 *payload = skb->data;
if (!inet->hdrincl)
......
......@@ -1049,7 +1049,10 @@ static void ip6_rt_update_pmtu(struct dst_entry *dst, u32 mtu)
{
struct rt6_info *rt6 = (struct rt6_info*)dst;
dst_confirm(dst);
if (mtu < dst_mtu(dst) && rt6->rt6i_dst.plen == 128) {
struct net *net = dev_net(dst->dev);
rt6->rt6i_flags |= RTF_MODIFIED;
if (mtu < IPV6_MIN_MTU) {
u32 features = dst_metric(dst, RTAX_FEATURES);
......@@ -1058,9 +1061,39 @@ static void ip6_rt_update_pmtu(struct dst_entry *dst, u32 mtu)
dst_metric_set(dst, RTAX_FEATURES, features);
}
dst_metric_set(dst, RTAX_MTU, mtu);
rt6_update_expires(rt6, net->ipv6.sysctl.ip6_rt_mtu_expires);
}
}
void ip6_update_pmtu(struct sk_buff *skb, struct net *net, u32 mtu,
int oif, __be32 mark)
{
const struct ipv6hdr *iph = (struct ipv6hdr *) skb->data;
struct dst_entry *dst;
struct flowi6 fl6;
memset(&fl6, 0, sizeof(fl6));
fl6.flowi6_oif = oif;
fl6.flowi6_mark = mark;
fl6.flowi6_flags = FLOWI_FLAG_PRECOW_METRICS;
fl6.daddr = iph->daddr;
fl6.saddr = iph->saddr;
fl6.flowlabel = (*(__be32 *) iph) & IPV6_FLOWINFO_MASK;
dst = ip6_route_output(net, NULL, &fl6);
if (!dst->error)
ip6_rt_update_pmtu(dst, ntohl(mtu));
dst_release(dst);
}
EXPORT_SYMBOL_GPL(ip6_update_pmtu);
void ip6_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, __be32 mtu)
{
ip6_update_pmtu(skb, sock_net(sk), mtu,
sk->sk_bound_dev_if, sk->sk_mark);
}
EXPORT_SYMBOL_GPL(ip6_sk_update_pmtu);
static unsigned int ip6_default_advmss(const struct dst_entry *dst)
{
struct net_device *dev = dst->dev;
......@@ -1703,116 +1736,6 @@ out:
dst_release(&rt->dst);
}
/*
* Handle ICMP "packet too big" messages
* i.e. Path MTU discovery
*/
static void rt6_do_pmtu_disc(const struct in6_addr *daddr, const struct in6_addr *saddr,
struct net *net, u32 pmtu, int ifindex)
{
struct rt6_info *rt, *nrt;
int allfrag = 0;
again:
rt = rt6_lookup(net, daddr, saddr, ifindex, 0);
if (!rt)
return;
if (rt6_check_expired(rt)) {
ip6_del_rt(rt);
goto again;
}
if (pmtu >= dst_mtu(&rt->dst))
goto out;
if (pmtu < IPV6_MIN_MTU) {
/*
* According to RFC2460, PMTU is set to the IPv6 Minimum Link
* MTU (1280) and a fragment header should always be included
* after a node receiving Too Big message reporting PMTU is
* less than the IPv6 Minimum Link MTU.
*/
pmtu = IPV6_MIN_MTU;
allfrag = 1;
}
/* New mtu received -> path was valid.
They are sent only in response to data packets,
so that this nexthop apparently is reachable. --ANK
*/
dst_confirm(&rt->dst);
/* Host route. If it is static, it would be better
not to override it, but add new one, so that
when cache entry will expire old pmtu
would return automatically.
*/
if (rt->rt6i_flags & RTF_CACHE) {
dst_metric_set(&rt->dst, RTAX_MTU, pmtu);
if (allfrag) {
u32 features = dst_metric(&rt->dst, RTAX_FEATURES);
features |= RTAX_FEATURE_ALLFRAG;
dst_metric_set(&rt->dst, RTAX_FEATURES, features);
}
rt6_update_expires(rt, net->ipv6.sysctl.ip6_rt_mtu_expires);
rt->rt6i_flags |= RTF_MODIFIED;
goto out;
}
/* Network route.
Two cases are possible:
1. It is connected route. Action: COW
2. It is gatewayed route or NONEXTHOP route. Action: clone it.
*/
if (!dst_get_neighbour_noref_raw(&rt->dst) && !(rt->rt6i_flags & RTF_NONEXTHOP))
nrt = rt6_alloc_cow(rt, daddr, saddr);
else
nrt = rt6_alloc_clone(rt, daddr);
if (nrt) {
dst_metric_set(&nrt->dst, RTAX_MTU, pmtu);
if (allfrag) {
u32 features = dst_metric(&nrt->dst, RTAX_FEATURES);
features |= RTAX_FEATURE_ALLFRAG;
dst_metric_set(&nrt->dst, RTAX_FEATURES, features);
}
/* According to RFC 1981, detecting PMTU increase shouldn't be
* happened within 5 mins, the recommended timer is 10 mins.
* Here this route expiration time is set to ip6_rt_mtu_expires
* which is 10 mins. After 10 mins the decreased pmtu is expired
* and detecting PMTU increase will be automatically happened.
*/
rt6_update_expires(nrt, net->ipv6.sysctl.ip6_rt_mtu_expires);
nrt->rt6i_flags |= RTF_DYNAMIC;
ip6_ins_rt(nrt);
}
out:
dst_release(&rt->dst);
}
void rt6_pmtu_discovery(const struct in6_addr *daddr, const struct in6_addr *saddr,
struct net_device *dev, u32 pmtu)
{
struct net *net = dev_net(dev);
/*
* RFC 1981 states that a node "MUST reduce the size of the packets it
* is sending along the path" that caused the Packet Too Big message.
* Since it's not possible in the general case to determine which
* interface was used to send the original packet, we update the MTU
* on the interface that will be used to send future packets. We also
* update the MTU on the interface that received the Packet Too Big in
* case the original packet was forced out that interface with
* SO_BINDTODEVICE or similar. This is the next best thing to the
* correct behaviour, which would be to update the MTU on all
* interfaces.
*/
rt6_do_pmtu_disc(daddr, saddr, net, pmtu, 0);
rt6_do_pmtu_disc(daddr, saddr, net, pmtu, dev->ifindex);
}
/*
* Misc support functions
*/
......
......@@ -415,6 +415,8 @@ static void tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
} else
dst_hold(dst);
dst->ops->update_pmtu(dst, ntohl(info));
if (inet_csk(sk)->icsk_pmtu_cookie > dst_mtu(dst)) {
tcp_sync_mss(sk, dst_mtu(dst));
tcp_simple_retransmit(sk);
......
......@@ -479,6 +479,9 @@ void __udp6_lib_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
if (sk == NULL)
return;
if (type == ICMPV6_PKT_TOOBIG)
ip6_sk_update_pmtu(skb, sk, info);
np = inet6_sk(sk);
if (!icmpv6_err_convert(type, code, &err) && !np->recverr)
......
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