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Commit d894ba18 authored by Craig Gallek's avatar Craig Gallek Committed by David S. Miller
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soreuseport: fix ordering for mixed v4/v6 sockets 



With the SO_REUSEPORT socket option, it is possible to create sockets
in the AF_INET and AF_INET6 domains which are bound to the same IPv4 address.
This is only possible with SO_REUSEPORT and when not using IPV6_V6ONLY on
the AF_INET6 sockets.

Prior to the commits referenced below, an incoming IPv4 packet would
always be routed to a socket of type AF_INET when this mixed-mode was used.
After those changes, the same packet would be routed to the most recently
bound socket (if this happened to be an AF_INET6 socket, it would
have an IPv4 mapped IPv6 address).

The change in behavior occurred because the recent SO_REUSEPORT optimizations
short-circuit the socket scoring logic as soon as they find a match.  They
did not take into account the scoring logic that favors AF_INET sockets
over AF_INET6 sockets in the event of a tie.

To fix this problem, this patch changes the insertion order of AF_INET
and AF_INET6 addresses in the TCP and UDP socket lists when the sockets
have SO_REUSEPORT set.  AF_INET sockets will be inserted at the head of the
list and AF_INET6 sockets with SO_REUSEPORT set will always be inserted at
the tail of the list.  This will force AF_INET sockets to always be
considered first.

Fixes: e32ea7e7 ("soreuseport: fast reuseport UDP socket selection")
Fixes: 125e80b88687 ("soreuseport: fast reuseport TCP socket selection")

Reported-by: default avatarMaciej Żenczykowski <maze@google.com>
Signed-off-by: default avatarCraig Gallek <kraig@google.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c5b5343c

include/linux/rculist_nulls.h

+39 −0
Original line number Diff line number Diff line
@@ -98,6 +98,45 @@ static inline void hlist_nulls_add_head_rcu(struct hlist_nulls_node *n, 
	if (!is_a_nulls(first))

		first->pprev = &n->next;

}



/**

 * hlist_nulls_add_tail_rcu

 * @n: the element to add to the hash list.

 * @h: the list to add to.

 *

 * Description:

 * Adds the specified element to the end of the specified hlist_nulls,

 * while permitting racing traversals.  NOTE: tail insertion requires

 * list traversal.

 *

 * The caller must take whatever precautions are necessary

 * (such as holding appropriate locks) to avoid racing

 * with another list-mutation primitive, such as hlist_nulls_add_head_rcu()

 * or hlist_nulls_del_rcu(), running on this same list.

 * However, it is perfectly legal to run concurrently with

 * the _rcu list-traversal primitives, such as

 * hlist_nulls_for_each_entry_rcu(), used to prevent memory-consistency

 * problems on Alpha CPUs.  Regardless of the type of CPU, the

 * list-traversal primitive must be guarded by rcu_read_lock().

 */

static inline void hlist_nulls_add_tail_rcu(struct hlist_nulls_node *n,

					struct hlist_nulls_head *h)

{

	struct hlist_nulls_node *i, *last = NULL;



	for (i = hlist_nulls_first_rcu(h); !is_a_nulls(i);

	     i = hlist_nulls_next_rcu(i))

		last = i;



	if (last) {

		n->next = last->next;

		n->pprev = &last->next;

		rcu_assign_pointer(hlist_nulls_next_rcu(last), n);

	} else {

		hlist_nulls_add_head_rcu(n, h);

	}

}



/**

 * hlist_nulls_for_each_entry_rcu - iterate over rcu list of given type

 * @tpos:	the type * to use as a loop cursor.

include/net/sock.h

+5 −1
Original line number Diff line number Diff line
@@ -630,6 +630,10 @@ static inline void sk_add_node_rcu(struct sock *sk, struct hlist_head *list) 


static inline void __sk_nulls_add_node_rcu(struct sock *sk, struct hlist_nulls_head *list)

{

	if (IS_ENABLED(CONFIG_IPV6) && sk->sk_reuseport &&

	    sk->sk_family == AF_INET6)

		hlist_nulls_add_tail_rcu(&sk->sk_nulls_node, list);

	else

		hlist_nulls_add_head_rcu(&sk->sk_nulls_node, list);

}

net/ipv4/udp.c

+7 −2
Original line number Diff line number Diff line
@@ -339,6 +339,11 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum, 


		hslot2 = udp_hashslot2(udptable, udp_sk(sk)->udp_portaddr_hash);

		spin_lock(&hslot2->lock);

		if (IS_ENABLED(CONFIG_IPV6) && sk->sk_reuseport &&

			sk->sk_family == AF_INET6)

			hlist_nulls_add_tail_rcu(&udp_sk(sk)->udp_portaddr_node,

						 &hslot2->head);

		else

			hlist_nulls_add_head_rcu(&udp_sk(sk)->udp_portaddr_node,

						 &hslot2->head);

		hslot2->count++;