tcp/dccp: warn user for preferred ip_local_port_range
authorEric Dumazet <edumazet@google.com>
Wed, 27 May 2015 18:34:37 +0000 (11:34 -0700)
committerDavid S. Miller <davem@davemloft.net>
Wed, 27 May 2015 18:35:36 +0000 (14:35 -0400)
After commit 07f4c90062f8f ("tcp/dccp: try to not exhaust
ip_local_port_range in connect()") it is advised to have an even number
of ports described in /proc/sys/net/ipv4/ip_local_port_range

This means start/end values should have a different parity.

Let's warn sysadmins of this, so that they can update their settings
if they want to.

Suggested-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
include/net/netns/ipv4.h
net/ipv4/sysctl_net_ipv4.c

index 6848b8bb2e6319ac9ddd90dd45b39eb01c6c9ff8..c68926b4899c36e77c38b6244dfb8d126685b905 100644 (file)
@@ -19,6 +19,7 @@ struct sock;
 struct local_ports {
        seqlock_t       lock;
        int             range[2];
+       bool            warned;
 };
 
 struct ping_group_range {
index e64892769607a6089e10d5c9e63dc3564c983341..0330ab2e2b6329ced120cd9b7100a5a34f50e82b 100644 (file)
@@ -45,7 +45,13 @@ static int ip_ping_group_range_max[] = { GID_T_MAX, GID_T_MAX };
 /* Update system visible IP port range */
 static void set_local_port_range(struct net *net, int range[2])
 {
+       bool same_parity = !((range[0] ^ range[1]) & 1);
+
        write_seqlock(&net->ipv4.ip_local_ports.lock);
+       if (same_parity && !net->ipv4.ip_local_ports.warned) {
+               net->ipv4.ip_local_ports.warned = true;
+               pr_err_ratelimited("ip_local_port_range: prefer different parity for start/end values.\n");
+       }
        net->ipv4.ip_local_ports.range[0] = range[0];
        net->ipv4.ip_local_ports.range[1] = range[1];
        write_sequnlock(&net->ipv4.ip_local_ports.lock);