Commit b406472b authored by Paolo Abeni's avatar Paolo Abeni Committed by David S. Miller
Browse files

net: ipv4: avoid mixed n_redirects and rate_tokens usage

Since commit c09551c6

 ("net: ipv4: use a dedicated counter
for icmp_v4 redirect packets") we use 'n_redirects' to account
for redirect packets, but we still use 'rate_tokens' to compute
the redirect packets exponential backoff.

If the device sent to the relevant peer any ICMP error packet
after sending a redirect, it will also update 'rate_token' according
to the leaking bucket schema; typically 'rate_token' will raise
above BITS_PER_LONG and the redirect packets backoff algorithm
will produce undefined behavior.

Fix the issue using 'n_redirects' to compute the exponential backoff
in ip_rt_send_redirect().

Note that we still clear rate_tokens after a redirect silence period,
to avoid changing an established behaviour.

The root cause predates git history; before the mentioned commit in
the critical scenario, the kernel stopped sending redirects, after
the mentioned commit the behavior more randomic.

Reported-by: default avatarXiumei Mu <>
Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Fixes: c09551c6

 ("net: ipv4: use a dedicated counter for icmp_v4 redirect packets")
Signed-off-by: default avatarPaolo Abeni <>
Acked-by: default avatarLorenzo Bianconi <>
Signed-off-by: default avatarDavid S. Miller <>
parent a54cdeeb
......@@ -916,16 +916,15 @@ void ip_rt_send_redirect(struct sk_buff *skb)
if (peer->rate_tokens == 0 ||
(peer->rate_last +
(ip_rt_redirect_load << peer->rate_tokens)))) {
(ip_rt_redirect_load << peer->n_redirects)))) {
__be32 gw = rt_nexthop(rt, ip_hdr(skb)->daddr);
icmp_send(skb, ICMP_REDIRECT, ICMP_REDIR_HOST, gw);
peer->rate_last = jiffies;
if (log_martians &&
peer->rate_tokens == ip_rt_redirect_number)
peer->n_redirects == ip_rt_redirect_number)
net_warn_ratelimited("host %pI4/if%d ignores redirects for %pI4 to %pI4\n",
&ip_hdr(skb)->saddr, inet_iif(skb),
&ip_hdr(skb)->daddr, &gw);
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