From d894ba18d4e449b3a7f6eb491f16c9e02933736e Mon Sep 17 00:00:00 2001 From: Craig Gallek Date: Tue, 12 Apr 2016 13:11:25 -0400 Subject: [PATCH] soreuseport: fix ordering for mixed v4/v6 sockets MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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: e32ea7e74727 ("soreuseport: fast reuseport UDP socket selection") Fixes: 125e80b88687 ("soreuseport: fast reuseport TCP socket selection") Reported-by: Maciej Żenczykowski Signed-off-by: Craig Gallek Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/linux/rculist_nulls.h | 39 +++++++++++++++++++++++++++++++++++ include/net/sock.h | 6 +++++- net/ipv4/udp.c | 9 ++++++-- 3 files changed, 51 insertions(+), 3 deletions(-) diff --git a/include/linux/rculist_nulls.h b/include/linux/rculist_nulls.h index 1c33dd7da4a7..4ae95f7e8597 100644 --- a/include/linux/rculist_nulls.h +++ b/include/linux/rculist_nulls.h @@ -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. diff --git a/include/net/sock.h b/include/net/sock.h index 255d3e03727b..121ffc115c4f 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -630,7 +630,11 @@ 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) { - hlist_nulls_add_head_rcu(&sk->sk_nulls_node, 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); } static inline void sk_nulls_add_node_rcu(struct sock *sk, struct hlist_nulls_head *list) diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index 08eed5e16df0..a2e7f55a1f61 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -339,8 +339,13 @@ found: hslot2 = udp_hashslot2(udptable, udp_sk(sk)->udp_portaddr_hash); spin_lock(&hslot2->lock); - hlist_nulls_add_head_rcu(&udp_sk(sk)->udp_portaddr_node, - &hslot2->head); + 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++; spin_unlock(&hslot2->lock); } -- 2.20.1