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[INET]: local port range robustness

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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>
This commit is contained in:
Stephen Hemminger
2007-10-10 17:30:46 -07:00
committed by David S. Miller
parent 0639300900
commit 227b60f510
10 changed files with 146 additions and 58 deletions
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13
net/ipv4/inet_hashtables.c
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@@ -279,19 +279,18 @@ int inet_hash_connect(struct inet_timewait_death_row *death_row,
int ret;
if (!snum) {
int low = sysctl_local_port_range[0];
int high = sysctl_local_port_range[1];
int range = high - low;
int i;
int port;
int i, remaining, low, high, port;
static u32 hint;
u32 offset = hint + inet_sk_port_offset(sk);
struct hlist_node *node;
struct inet_timewait_sock *tw = NULL;
inet_get_local_port_range(&low, &high);
remaining = high - low;
local_bh_disable();
for (i = 1; i <= range; i++) {
port = low + (i + offset) % range;
for (i = 1; i <= remaining; i++) {
port = low + (i + offset) % remaining;
head = &hinfo->bhash[inet_bhashfn(port, hinfo->bhash_size)];
spin_lock(&head->lock);