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Merge branch 'ipv6-dgram-dst-cache'
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Martin KaFai Lau says:

====================
ipv6: datagram: Update dst cache of a connected udp sk during pmtu update

v2:
~ Protect __sk_dst_get() operations with rcu_read_lock in
  release_cb() because another thread may do ip6_dst_store()
  for a udp sk without taking the sk lock (e.g. in sendmsg).
~ Do a ipv6_addr_v4mapped(&sk->sk_v6_daddr) check before
  calling ip6_datagram_dst_update() in patch 3 and 4.  It is
  similar to how __ip6_datagram_connect handles it.
~ One fix in ip6_datagram_dst_update() in patch 2.  It needs
  to check (np->flow_label & IPV6_FLOWLABEL_MASK) before
  doing fl6_sock_lookup.  I was confused with the naming
  of IPV6_FLOWLABEL_MASK and IPV6_FLOWINFO_MASK.
~ Check dst->obsolete just on the safe side, although I think it
  should at least have DST_OBSOLETE_FORCE_CHK by now.
~ Add Fixes tag to patch 3 and 4
~ Add some points from the previous discussion about holding
  sk lock to the commit message in patch 3.

v1:
There is a case in connected UDP socket such that
getsockopt(IPV6_MTU) will return a stale MTU value. The reproducible
sequence could be the following:
1. Create a connected UDP socket
2. Send some datagrams out
3. Receive a ICMPV6_PKT_TOOBIG
4. No new outgoing datagrams to trigger the sk_dst_check()
   logic to update the sk->sk_dst_cache.
5. getsockopt(IPV6_MTU) returns the mtu from the invalid
   sk->sk_dst_cache instead of the newly created RTF_CACHE clone.

Patch 1 and 2 are the prep work.
Patch 3 and 4 are the fixes.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
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David S. Miller committed Apr 14, 2016
2 parents f1d0540 + e646b65 commit 97cc931
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Showing 4 changed files with 121 additions and 63 deletions.
2 changes: 2 additions & 0 deletions include/net/ipv6.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -959,6 +959,8 @@ int compat_ipv6_getsockopt(struct sock *sk, int level, int optname,
int ip6_datagram_connect(struct sock *sk, struct sockaddr *addr, int addr_len);
int ip6_datagram_connect_v6_only(struct sock *sk, struct sockaddr *addr,
int addr_len);
int ip6_datagram_dst_update(struct sock *sk, bool fix_sk_saddr);
void ip6_datagram_release_cb(struct sock *sk);

int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len,
int *addr_len);
Expand Down
169 changes: 106 additions & 63 deletions net/ipv6/datagram.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -40,18 +40,114 @@ static bool ipv6_mapped_addr_any(const struct in6_addr *a)
return ipv6_addr_v4mapped(a) && (a->s6_addr32[3] == 0);
}

static void ip6_datagram_flow_key_init(struct flowi6 *fl6, struct sock *sk)
{
struct inet_sock *inet = inet_sk(sk);
struct ipv6_pinfo *np = inet6_sk(sk);

memset(fl6, 0, sizeof(*fl6));
fl6->flowi6_proto = sk->sk_protocol;
fl6->daddr = sk->sk_v6_daddr;
fl6->saddr = np->saddr;
fl6->flowi6_oif = sk->sk_bound_dev_if;
fl6->flowi6_mark = sk->sk_mark;
fl6->fl6_dport = inet->inet_dport;
fl6->fl6_sport = inet->inet_sport;
fl6->flowlabel = np->flow_label;

if (!fl6->flowi6_oif)
fl6->flowi6_oif = np->sticky_pktinfo.ipi6_ifindex;

if (!fl6->flowi6_oif && ipv6_addr_is_multicast(&fl6->daddr))
fl6->flowi6_oif = np->mcast_oif;

security_sk_classify_flow(sk, flowi6_to_flowi(fl6));
}

int ip6_datagram_dst_update(struct sock *sk, bool fix_sk_saddr)
{
struct ip6_flowlabel *flowlabel = NULL;
struct in6_addr *final_p, final;
struct ipv6_txoptions *opt;
struct dst_entry *dst;
struct inet_sock *inet = inet_sk(sk);
struct ipv6_pinfo *np = inet6_sk(sk);
struct flowi6 fl6;
int err = 0;

if (np->sndflow && (np->flow_label & IPV6_FLOWLABEL_MASK)) {
flowlabel = fl6_sock_lookup(sk, np->flow_label);
if (!flowlabel)
return -EINVAL;
}
ip6_datagram_flow_key_init(&fl6, sk);

rcu_read_lock();
opt = flowlabel ? flowlabel->opt : rcu_dereference(np->opt);
final_p = fl6_update_dst(&fl6, opt, &final);
rcu_read_unlock();

dst = ip6_dst_lookup_flow(sk, &fl6, final_p);
if (IS_ERR(dst)) {
err = PTR_ERR(dst);
goto out;
}

if (fix_sk_saddr) {
if (ipv6_addr_any(&np->saddr))
np->saddr = fl6.saddr;

if (ipv6_addr_any(&sk->sk_v6_rcv_saddr)) {
sk->sk_v6_rcv_saddr = fl6.saddr;
inet->inet_rcv_saddr = LOOPBACK4_IPV6;
if (sk->sk_prot->rehash)
sk->sk_prot->rehash(sk);
}
}

ip6_dst_store(sk, dst,
ipv6_addr_equal(&fl6.daddr, &sk->sk_v6_daddr) ?
&sk->sk_v6_daddr : NULL,
#ifdef CONFIG_IPV6_SUBTREES
ipv6_addr_equal(&fl6.saddr, &np->saddr) ?
&np->saddr :
#endif
NULL);

out:
fl6_sock_release(flowlabel);
return err;
}

void ip6_datagram_release_cb(struct sock *sk)
{
struct dst_entry *dst;

if (ipv6_addr_v4mapped(&sk->sk_v6_daddr))
return;

rcu_read_lock();
dst = __sk_dst_get(sk);
if (!dst || !dst->obsolete ||
dst->ops->check(dst, inet6_sk(sk)->dst_cookie)) {
rcu_read_unlock();
return;
}
rcu_read_unlock();

ip6_datagram_dst_update(sk, false);
}
EXPORT_SYMBOL_GPL(ip6_datagram_release_cb);

static int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
{
struct sockaddr_in6 *usin = (struct sockaddr_in6 *) uaddr;
struct inet_sock *inet = inet_sk(sk);
struct ipv6_pinfo *np = inet6_sk(sk);
struct in6_addr *daddr, *final_p, final;
struct dst_entry *dst;
struct flowi6 fl6;
struct ip6_flowlabel *flowlabel = NULL;
struct ipv6_txoptions *opt;
struct in6_addr *daddr;
int addr_type;
int err;
__be32 fl6_flowlabel = 0;

if (usin->sin6_family == AF_INET) {
if (__ipv6_only_sock(sk))
Expand All @@ -66,15 +162,8 @@ static int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int a
if (usin->sin6_family != AF_INET6)
return -EAFNOSUPPORT;

memset(&fl6, 0, sizeof(fl6));
if (np->sndflow) {
fl6.flowlabel = usin->sin6_flowinfo&IPV6_FLOWINFO_MASK;
if (fl6.flowlabel&IPV6_FLOWLABEL_MASK) {
flowlabel = fl6_sock_lookup(sk, fl6.flowlabel);
if (!flowlabel)
return -EINVAL;
}
}
if (np->sndflow)
fl6_flowlabel = usin->sin6_flowinfo & IPV6_FLOWINFO_MASK;

addr_type = ipv6_addr_type(&usin->sin6_addr);

Expand Down Expand Up @@ -145,7 +234,7 @@ static int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int a
}

sk->sk_v6_daddr = *daddr;
np->flow_label = fl6.flowlabel;
np->flow_label = fl6_flowlabel;

inet->inet_dport = usin->sin6_port;

Expand All @@ -154,59 +243,13 @@ static int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int a
* destination cache for it.
*/

fl6.flowi6_proto = sk->sk_protocol;
fl6.daddr = sk->sk_v6_daddr;
fl6.saddr = np->saddr;
fl6.flowi6_oif = sk->sk_bound_dev_if;
fl6.flowi6_mark = sk->sk_mark;
fl6.fl6_dport = inet->inet_dport;
fl6.fl6_sport = inet->inet_sport;

if (!fl6.flowi6_oif)
fl6.flowi6_oif = np->sticky_pktinfo.ipi6_ifindex;

if (!fl6.flowi6_oif && (addr_type&IPV6_ADDR_MULTICAST))
fl6.flowi6_oif = np->mcast_oif;

security_sk_classify_flow(sk, flowi6_to_flowi(&fl6));

rcu_read_lock();
opt = flowlabel ? flowlabel->opt : rcu_dereference(np->opt);
final_p = fl6_update_dst(&fl6, opt, &final);
rcu_read_unlock();

dst = ip6_dst_lookup_flow(sk, &fl6, final_p);
err = 0;
if (IS_ERR(dst)) {
err = PTR_ERR(dst);
err = ip6_datagram_dst_update(sk, true);
if (err)
goto out;
}

/* source address lookup done in ip6_dst_lookup */

if (ipv6_addr_any(&np->saddr))
np->saddr = fl6.saddr;

if (ipv6_addr_any(&sk->sk_v6_rcv_saddr)) {
sk->sk_v6_rcv_saddr = fl6.saddr;
inet->inet_rcv_saddr = LOOPBACK4_IPV6;
if (sk->sk_prot->rehash)
sk->sk_prot->rehash(sk);
}

ip6_dst_store(sk, dst,
ipv6_addr_equal(&fl6.daddr, &sk->sk_v6_daddr) ?
&sk->sk_v6_daddr : NULL,
#ifdef CONFIG_IPV6_SUBTREES
ipv6_addr_equal(&fl6.saddr, &np->saddr) ?
&np->saddr :
#endif
NULL);

sk->sk_state = TCP_ESTABLISHED;
sk_set_txhash(sk);
out:
fl6_sock_release(flowlabel);
return err;
}

Expand Down
12 changes: 12 additions & 0 deletions net/ipv6/route.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1418,8 +1418,20 @@ EXPORT_SYMBOL_GPL(ip6_update_pmtu);

void ip6_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, __be32 mtu)
{
struct dst_entry *dst;

ip6_update_pmtu(skb, sock_net(sk), mtu,
sk->sk_bound_dev_if, sk->sk_mark);

dst = __sk_dst_get(sk);
if (!dst || !dst->obsolete ||
dst->ops->check(dst, inet6_sk(sk)->dst_cookie))
return;

bh_lock_sock(sk);
if (!sock_owned_by_user(sk) && !ipv6_addr_v4mapped(&sk->sk_v6_daddr))
ip6_datagram_dst_update(sk, false);
bh_unlock_sock(sk);
}
EXPORT_SYMBOL_GPL(ip6_sk_update_pmtu);

Expand Down
1 change: 1 addition & 0 deletions net/ipv6/udp.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1539,6 +1539,7 @@ struct proto udpv6_prot = {
.sendmsg = udpv6_sendmsg,
.recvmsg = udpv6_recvmsg,
.backlog_rcv = __udpv6_queue_rcv_skb,
.release_cb = ip6_datagram_release_cb,
.hash = udp_lib_hash,
.unhash = udp_lib_unhash,
.rehash = udp_v6_rehash,
Expand Down

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