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udp: Improve load balancing for SO_REUSEPORT.

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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: acdcecc612 ("udp: correct reuseport selection with connected sockets")
CC: Willem de Bruijn <willemb@google.com>
Reviewed-by: Benjamin Herrenschmidt <benh@amazon.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Kuniyuki Iwashima 2020-07-21 15:15:31 +09:00 committed by David S. Miller
parent f2b2c55e51
commit efc6b6f6c3
2 changed files with 18 additions and 12 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

13
net/ipv4/udp.c
View file

@ -416,7 +416,7 @@ 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;
@ -426,17 +426,20 @@ static struct sock *udp4_lib_lookup2(struct net *net,
score = compute_score(sk, net, saddr, sport,
daddr, hnum, dif, sdif);
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;

13
net/ipv6/udp.c
View file

@ -148,7 +148,7 @@ static struct sock *udp6_lib_lookup2(struct net *net,
int dif, int sdif, struct udp_hslot *hslot2,
struct sk_buff *skb)
{
struct sock *sk, *result;
struct sock *sk, *result, *reuseport_result;
int score, badness;
u32 hash = 0;
@ -158,17 +158,20 @@ static struct sock *udp6_lib_lookup2(struct net *net,
score = compute_score(sk, net, saddr, sport,
daddr, hnum, dif, sdif);
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;
}
}