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Commit 325ac51b authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Greg Kroah-Hartman
Browse files

udp: Improve load balancing for SO_REUSEPORT. 



[ Upstream commit efc6b6f6c3113e8b203b9debfb72d81e0f3dcace ]

Currently, SO_REUSEPORT does not work well if connected sockets are in a
UDP reuseport group.

Then reuseport_has_conns() returns true and the result of
reuseport_select_sock() is discarded. Also, unconnected sockets have the
same score, hence only does the first unconnected socket in udp_hslot
always receive all packets sent to unconnected sockets.

So, the result of reuseport_select_sock() should be used for load
balancing.

The noteworthy point is that the unconnected sockets placed after
connected sockets in sock_reuseport.socks will receive more packets than
others because of the algorithm in reuseport_select_sock().

    index | connected | reciprocal_scale | result
    ---------------------------------------------
    0     | no        | 20%              | 40%
    1     | no        | 20%              | 20%
    2     | yes       | 20%              | 0%
    3     | no        | 20%              | 40%
    4     | yes       | 20%              | 0%

If most of the sockets are connected, this can be a problem, but it still
works better than now.

Fixes: acdcecc61285 ("udp: correct reuseport selection with connected sockets")
CC: Willem de Bruijn <willemb@google.com>
Reviewed-by: default avatarBenjamin Herrenschmidt <benh@amazon.com>
Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.co.jp>
Acked-by: default avatarWillem de Bruijn <willemb@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 0f26f967

net/ipv4/udp.c

+9 −6
Original line number Diff line number Diff line
@@ -433,7 +433,7 @@ static struct sock *udp4_lib_lookup2(struct net *net, 
				     struct udp_hslot *hslot2,

				     struct sk_buff *skb)

{

	struct sock *sk, *result;

	struct sock *sk, *result, *reuseport_result;

	int score, badness;

	u32 hash = 0;
@@ -443,17 +443,20 @@ static struct sock *udp4_lib_lookup2(struct net *net, 
		score = compute_score(sk, net, saddr, sport,

				      daddr, hnum, dif, sdif, exact_dif);

		if (score > badness) {

			reuseport_result = NULL;



			if (sk->sk_reuseport &&

			    sk->sk_state != TCP_ESTABLISHED) {

				hash = udp_ehashfn(net, daddr, hnum,

						   saddr, sport);

				result = reuseport_select_sock(sk, hash, skb,

				reuseport_result = reuseport_select_sock(sk, hash, skb,

									 sizeof(struct udphdr));

				if (result && !reuseport_has_conns(sk, false))

					return result;

				if (reuseport_result && !reuseport_has_conns(sk, false))

					return reuseport_result;

			}



			result = reuseport_result ? : sk;

			badness = score;

			result = sk;

		}

	}

	return result;

net/ipv6/udp.c

+9 −6
Original line number Diff line number Diff line
@@ -167,7 +167,7 @@ static struct sock *udp6_lib_lookup2(struct net *net, 
		int dif, int sdif, bool exact_dif,

		struct udp_hslot *hslot2, struct sk_buff *skb)

{

	struct sock *sk, *result;

	struct sock *sk, *result, *reuseport_result;

	int score, badness;

	u32 hash = 0;
@@ -177,17 +177,20 @@ static struct sock *udp6_lib_lookup2(struct net *net, 
		score = compute_score(sk, net, saddr, sport,

				      daddr, hnum, dif, sdif, exact_dif);

		if (score > badness) {

			reuseport_result = NULL;



			if (sk->sk_reuseport &&

			    sk->sk_state != TCP_ESTABLISHED) {

				hash = udp6_ehashfn(net, daddr, hnum,

						    saddr, sport);



				result = reuseport_select_sock(sk, hash, skb,

				reuseport_result = reuseport_select_sock(sk, hash, skb,

									 sizeof(struct udphdr));

				if (result && !reuseport_has_conns(sk, false))

					return result;

				if (reuseport_result && !reuseport_has_conns(sk, false))

					return reuseport_result;

			}

			result = sk;



			result = reuseport_result ? : sk;

			badness = score;

		}

	}