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Message-Id: <20230125195114.596295-1-haleyb.dev@gmail.com>
Date: Wed, 25 Jan 2023 14:51:14 -0500
From: Brian Haley <haleyb.dev@...il.com>
To: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
pabeni@...hat.com
Cc: netdev@...r.kernel.org
Subject: [PATCH net-next v2] neighbor: fix proxy_delay usage when it is zero
When set to zero, the neighbor sysctl proxy_delay value
does not cause an immediate reply for ARP/ND requests
as expected, it instead causes a random delay between
[0, U32_MAX]. Looking at this comment from
__get_random_u32_below() explains the reason:
/*
* This function is technically undefined for ceil == 0, and in fact
* for the non-underscored constant version in the header, we build bug
* on that. But for the non-constant case, it's convenient to have that
* evaluate to being a straight call to get_random_u32(), so that
* get_random_u32_inclusive() can work over its whole range without
* undefined behavior.
*/
Added helper function that does not call get_random_u32_below()
if proxy_delay is zero and just uses the current value of
jiffies instead, causing pneigh_enqueue() to respond
immediately.
Also added definition of proxy_delay to ip-sysctl.txt since
it was missing.
Signed-off-by: Brian Haley <haleyb.dev@...il.com>
---
Documentation/networking/ip-sysctl.rst | 8 ++++++++
net/core/neighbour.c | 14 ++++++++++++--
2 files changed, 20 insertions(+), 2 deletions(-)
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index 7fbd060d6047..58f74051e07b 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -1589,6 +1589,14 @@ proxy_arp_pvlan - BOOLEAN
Hewlett-Packard call it Source-Port filtering or port-isolation.
Ericsson call it MAC-Forced Forwarding (RFC Draft).
+proxy_delay - INTEGER
+ Delay proxy response.
+
+ Delay response to a neighbor solicitation when proxy_arp
+ or proxy_ndp is enabled. A random value between [0, proxy_delay]
+ will be chosen, setting to zero means reply with no delay.
+ Value in jiffies. Defaults to 80.
+
shared_media - BOOLEAN
Send(router) or accept(host) RFC1620 shared media redirects.
Overrides secure_redirects.
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index f00a79fc301b..57258110bccd 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1662,11 +1662,21 @@ static void neigh_proxy_process(struct timer_list *t)
spin_unlock(&tbl->proxy_queue.lock);
}
+static unsigned long neigh_proxy_delay(struct neigh_parms *p)
+{
+ /* If proxy_delay is zero, do not call get_random_u32_below()
+ * as it is undefined behavior.
+ */
+ unsigned long proxy_delay = NEIGH_VAR(p, PROXY_DELAY);
+
+ return proxy_delay ?
+ jiffies + get_random_u32_below(proxy_delay) : jiffies;
+}
+
void pneigh_enqueue(struct neigh_table *tbl, struct neigh_parms *p,
struct sk_buff *skb)
{
- unsigned long sched_next = jiffies +
- get_random_u32_below(NEIGH_VAR(p, PROXY_DELAY));
+ unsigned long sched_next = neigh_proxy_delay(p);
if (p->qlen > NEIGH_VAR(p, PROXY_QLEN)) {
kfree_skb(skb);
--
2.34.1
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