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authorEric Dumazet <edumazet@google.com>2015-05-20 10:59:02 -0700
committerDavid S. Miller <davem@davemloft.net>2015-05-21 18:55:32 -0400
commit946f9eb226c296da0d6c630bdad282ca11d77f60 (patch)
treee57418581cf0adc129548c9427730f70b84045da
parentf5af1f57a2914e290de40e2c93716da8885c4965 (diff)
downloadop-kernel-dev-946f9eb226c296da0d6c630bdad282ca11d77f60.zip
op-kernel-dev-946f9eb226c296da0d6c630bdad282ca11d77f60.tar.gz
tcp: improve REUSEADDR/NOREUSEADDR cohabitation
inet_csk_get_port() randomization effort tends to spread sockets on all the available range (ip_local_port_range) This is unfortunate because SO_REUSEADDR sockets have less requirements than non SO_REUSEADDR ones. If an application uses SO_REUSEADDR hint, it is to try to allow source ports being shared. So instead of picking a random port number in ip_local_port_range, lets try first in first half of the range. This gives more chances to use upper half of the range for the sockets with strong requirements (not using SO_REUSEADDR) Note this patch does not add a new sysctl, and only changes the way we try to pick port number. Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Marcelo Ricardo Leitner <mleitner@redhat.com> Cc: Flavio Leitner <fbl@redhat.com> Acked-by: Flavio Leitner <fbl@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/ipv4/inet_connection_sock.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index b95fb26..60021d0 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -99,6 +99,7 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum)
struct net *net = sock_net(sk);
int smallest_size = -1, smallest_rover;
kuid_t uid = sock_i_uid(sk);
+ int attempt_half = (sk->sk_reuse == SK_CAN_REUSE) ? 1 : 0;
local_bh_disable();
if (!snum) {
@@ -106,6 +107,14 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum)
again:
inet_get_local_port_range(net, &low, &high);
+ if (attempt_half) {
+ int half = low + ((high - low) >> 1);
+
+ if (attempt_half == 1)
+ high = half;
+ else
+ low = half;
+ }
remaining = (high - low) + 1;
smallest_rover = rover = prandom_u32() % remaining + low;
@@ -154,6 +163,11 @@ again:
snum = smallest_rover;
goto have_snum;
}
+ if (attempt_half == 1) {
+ /* OK we now try the upper half of the range */
+ attempt_half = 2;
+ goto again;
+ }
goto fail;
}
/* OK, here is the one we will use. HEAD is
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