Re: [PATCH] inetpeer: ensure to set the maximum tokens the first time

On Thu, 2012-09-27 at 14:33 +0200, Nicolas Dichtel wrote:

quoted

When jiffies wraps around (for example, 5 minutes after the boot, see
INITIAL_JIFFIES) and peer has just been created, now - peer->rate_last can be
< XRLIM_BURST_FACTOR * timeout, so token is not set to the maximum value, thus
some icmp packets can be unexpectedly dropped.

With this patch, it's still possible that last_rate and rate_tokens are 0 at the
same time after jiffies wraps round, but the probability is very low and the
only consequence is to let some ICMP packets bypass the filter.

Signed-off-by: Nicolas Dichtel <redacted>
---
  net/ipv4/inetpeer.c | 10 +++++++---
  1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index e1e0a4e..92fec02 100644
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c

@@ -559,10 +559,14 @@ bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout)

  	token = peer->rate_tokens;
  	now = jiffies;
-	token += now - peer->rate_last;
-	peer->rate_last = now;
-	if (token > XRLIM_BURST_FACTOR * timeout)
+	if (!peer->rate_last && !token)
  		token = XRLIM_BURST_FACTOR * timeout;
+	else {
+		token += now - peer->rate_last;
+		if (token > XRLIM_BURST_FACTOR * timeout)
+			token = XRLIM_BURST_FACTOR * timeout;
+	}
+	peer->rate_last = now;
  	if (token >= timeout) {
  		token -= timeout;
  		rc = true;

I am sorry I dont understand your patch at all.

Why not init rate_last to a more sensible value ?

diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index e1e0a4e..25ed555 100644
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c

@@ -510,7 +510,7 @@ relookup:
  					secure_ipv6_id(daddr->addr.a6));
  		p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
  		p->rate_tokens = 0;
-		p->rate_last = 0;
+		p->rate_last = jiffies;