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[TCP/DCCP]: Randomize port selection

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This patch randomizes the port selected on bind() for connections
to help with possible security attacks. It should also be faster
in most cases because there is no need for a global lock.

Signed-off-by: Stephen Hemminger <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
This commit is contained in:
Stephen Hemminger 2005-11-03 16:33:23 -08:00 • committed by Arnaldo Carvalho de Melo
commit 6df716340d
6 changed files with 10 additions and 56 deletions
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15
net/ipv6/tcp_ipv6.c
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@ -114,16 +114,9 @@ static int tcp_v6_get_port(struct sock *sk, unsigned short snum)
int low = sysctl_local_port_range[0];
int high = sysctl_local_port_range[1];
int remaining = (high - low) + 1;
int rover;
int rover = net_random() % (high - low) + low;
spin_lock(&tcp_hashinfo.portalloc_lock);
if (tcp_hashinfo.port_rover < low)
rover = low;
else
rover = tcp_hashinfo.port_rover;
do { rover++;
if (rover > high)
rover = low;
do {
head = &tcp_hashinfo.bhash[inet_bhashfn(rover, tcp_hashinfo.bhash_size)];
spin_lock(&head->lock);
inet_bind_bucket_for_each(tb, node, &head->chain)
@ -132,9 +125,9 @@ static int tcp_v6_get_port(struct sock *sk, unsigned short snum)
break;
next:
spin_unlock(&head->lock);
if (++rover > high)
rover = low;
} while (--remaining > 0);
tcp_hashinfo.port_rover = rover;
spin_unlock(&tcp_hashinfo.portalloc_lock);
/* Exhausted local port range during search? It is not
* possible for us to be holding one of the bind hash