[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>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/net/ip.h b/include/net/ip.h
index abf2820a1125..3af3ed9d320b 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -171,7 +171,8 @@ extern unsigned long snmp_fold_field(void *mib[], int offt);
 extern int snmp_mib_init(void *ptr[2], size_t mibsize, size_t mibalign);
 extern void snmp_mib_free(void *ptr[2]);
 
-extern int sysctl_local_port_range[2];
+extern void inet_get_local_port_range(int *low, int *high);
+
 extern int sysctl_ip_default_ttl;
 extern int sysctl_ip_nonlocal_bind;