Messages in this thread Patches in this message | | | Date | Tue, 22 Mar 2005 17:47:10 +0100 | Subject | [PATCH] optimize check in port-allocation code | From | (Folkert van Heusden) |
| |
Hi,
In the 2.6.11 code, I found this: static int tcp_v6_get_port(struct sock *sk, unsigned short snum) also in: static int tcp_v4_get_port(struct sock *sk, unsigned short snum) { ... if (snum == 0) { int low = sysctl_local_port_range[0]; int high = sysctl_local_port_range[1];
spin_lock(&tcp_portalloc_lock); rover = tcp_port_rover; do { rover++; if ((rover < low) || (rover > high)) rover = low;
That 'rover < low' check is redundant? ints are bigger then the maximum portnumber (65535) so when rover++ gets too high, the check for 'rover > high' will truncate it to low (in the next line) waaay before the int itself wraps. It is needed because tcp_port_rover might be < low before the function starts, in that case the check for <low can be taken out of the loop.
Patch:
diff -uNr net/ipv4/tcp_ipv4.c.org net/ipv4/tcp_ipv4.c --- net/ipv4/tcp_ipv4.c.org 2005-03-04 22:39:37.340950747 +0100 +++ net/ipv4/tcp_ipv4.c 2005-03-04 22:40:35.570059217 +0100 @@ -222,10 +222,13 @@ int rover;
spin_lock(&tcp_portalloc_lock); - rover = tcp_port_rover; + if (tcp_port_rover < low) + rover = low; + else + rover = tcp_port_rover; do { rover++; - if (rover < low || rover > high) + if (rover > high) rover = low; head = &tcp_bhash[tcp_bhashfn(rover)]; spin_lock(&head->lock); diff -uNr net/ipv6/tcp_ipv6.c.org net/ipv6/tcp_ipv6.c --- net/ipv6/tcp_ipv6.c.org 2005-03-04 22:41:44.043007791 +0100 +++ net/ipv6/tcp_ipv6.c 2005-03-04 22:42:17.604728073 +0100 @@ -139,9 +139,12 @@ int rover;
spin_lock(&tcp_portalloc_lock); - rover = tcp_port_rover; + if (tcp_port_rover < low) + rover = low; + else + rover = tcp_port_rover; do { rover++; - if ((rover < low) || (rover > high)) + if (rover > high) rover = low; head = &tcp_bhash[tcp_bhashfn(rover)]; spin_lock(&head->lock);
Signed-off-by: Folkert van Heusden <folkert@vanheusden.com>
Folkert van Heusden
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