On Wed, 2015-05-27 at 09:18 -0700, Eric Dumazet wrote:
> On Wed, 2015-05-27 at 18:25 +0300, Crestez Dan Leonard wrote:
> > Hello,
> >
> > I'm confused about the port_offset parameter to __inet_hash_connect.
> >
> > When allocating the local port for an outgoing TCP connection the port
> > search looks something like this:
> >
> > static u32 hint;
> > u32 offset = hint + port_offset;
> >
> > inet_get_local_port_range(net, &low, &high);
> > remaining = (high - low) + 1;
> >
> > for (i = 1; i <= remaining; i++) {
> > port = low + (i + offset) % remaining;
> > /* check port is free */
> >
> > The port_offset is calculated for v4 and v6 based on a hash of src/dst
> > addresses, presumably in order to improve security.
> >
> > I see a few issues with this:
> > - The port_offset is calculated even if the local port was already
> > assigned via bind. This wastes a few cycles.
>
> OK. Not a big deal I guess.
Patch for IPv4 would be :
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index
185efef0f1251ba9d45fabb3ed51777a8be097a6..be4bac368b6bfb8a1eca429cce415da99adc5515
100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -594,7 +594,11 @@ out:
int inet_hash_connect(struct inet_timewait_death_row *death_row,
struct sock *sk)
{
- return __inet_hash_connect(death_row, sk, inet_sk_port_offset(sk),
+ u32 port_offset = 0;
+
+ if (!inet_sk(sk)->inet_num)
+ port_offset = inet_sk_port_offset(sk);
+ return __inet_hash_connect(death_row, sk, port_offset,
__inet_check_established);
}
EXPORT_SYMBOL_GPL(inet_hash_connect);
--
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