diff options
| author | Brian Haley <haleyb.dev@gmail.com> | 2023-01-30 12:14:28 -0500 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2023-02-01 21:02:54 -0800 |
| commit | 62e395f82d04510b0f86e5e603e29412be88596f (patch) | |
| tree | 0389f920c74480c2b9d32661450987891fa7f979 | |
| parent | 983f507c3043e90b2c6429cd67903c4ca8208b5c (diff) | |
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@gmail.com>
Link: https://lore.kernel.org/r/20230130171428.367111-1-haleyb.dev@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | Documentation/networking/ip-sysctl.rst | 8 | ||||
| -rw-r--r-- | 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 39df3cfb3bcb..87dd1c5283e6 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -1592,6 +1592,14 @@ 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); |