[INET]: local port range robustness
Expansion of original idea from Denis V. Lunev <den@openvz.org>
Add robustness and locking to the local_port_range sysctl.
1. Enforce that low < high when setting.
2. Use seqlock to ensure atomic update.
The locking might seem like overkill, but there are
cases where sysadmin might want to change value in the
middle of a DoS attack.
Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index ef4d901..cb9fc58 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -147,11 +147,11 @@
write_lock_bh(&udp_hash_lock);
if (!snum) {
- int i;
- int low = sysctl_local_port_range[0];
- int high = sysctl_local_port_range[1];
+ int i, low, high;
unsigned rover, best, best_size_so_far;
+ inet_get_local_port_range(&low, &high);
+
best_size_so_far = UINT_MAX;
best = rover = net_random() % (high - low) + low;