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kernel: fix bridge proxyarp issue with some broken DHCP clients

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There are broken devices in the wild that handle duplicate IP address
detection by sending out ARP requests for the IP that they received from a
DHCP server and refuse the address if they get a reply.
When proxyarp is enabled, they would go into a loop of requesting an address
and then NAKing it again.

Fixes: https://github.com/openwrt/openwrt/issues/14309
Signed-off-by: Felix Fietkau <nbd@nbd.name>
This commit is contained in:
Felix Fietkau 2024-01-05 11:58:15 +01:00
parent 4a5d1d0e95
commit c1ad78318c
2 changed files with 74 additions and 0 deletions
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37
target/linux/generic/pending-5.15/151-net-bridge-do-not-send-arp-replies-if-src-and-target.patch Normal file
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@ -0,0 +1,37 @@
From: Felix Fietkau <nbd@nbd.name>
Date: Thu, 4 Jan 2024 15:21:21 +0100
Subject: [PATCH] net: bridge: do not send arp replies if src and target hw
addr is the same
There are broken devices in the wild that handle duplicate IP address
detection by sending out ARP requests for the IP that they received from a
DHCP server and refuse the address if they get a reply.
When proxyarp is enabled, they would go into a loop of requesting an address
and then NAKing it again.
Link: https://github.com/openwrt/openwrt/issues/14309
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
--- a/net/bridge/br_arp_nd_proxy.c
+++ b/net/bridge/br_arp_nd_proxy.c
@@ -204,7 +204,10 @@ void br_do_proxy_suppress_arp(struct sk_
if ((p && (p->flags & BR_PROXYARP)) ||
(f->dst && (f->dst->flags & (BR_PROXYARP_WIFI |
BR_NEIGH_SUPPRESS)))) {
- if (!vid)
+ replied = true;
+ if (!memcmp(n->ha, sha, dev->addr_len))
+ replied = false;
+ else if (!vid)
br_arp_send(br, p, skb->dev, sip, tip,
sha, n->ha, sha, 0, 0);
else
@@ -212,7 +215,6 @@ void br_do_proxy_suppress_arp(struct sk_
sha, n->ha, sha,
skb->vlan_proto,
skb_vlan_tag_get(skb));
- replied = true;
}
/* If we have replied or as long as we know the

37
target/linux/generic/pending-6.1/151-net-bridge-do-not-send-arp-replies-if-src-and-target.patch Normal file
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@ -0,0 +1,37 @@
From: Felix Fietkau <nbd@nbd.name>
Date: Thu, 4 Jan 2024 15:21:21 +0100
Subject: [PATCH] net: bridge: do not send arp replies if src and target hw
addr is the same
There are broken devices in the wild that handle duplicate IP address
detection by sending out ARP requests for the IP that they received from a
DHCP server and refuse the address if they get a reply.
When proxyarp is enabled, they would go into a loop of requesting an address
and then NAKing it again.
Link: https://github.com/openwrt/openwrt/issues/14309
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
--- a/net/bridge/br_arp_nd_proxy.c
+++ b/net/bridge/br_arp_nd_proxy.c
@@ -204,7 +204,10 @@ void br_do_proxy_suppress_arp(struct sk_
if ((p && (p->flags & BR_PROXYARP)) ||
(f->dst && (f->dst->flags & (BR_PROXYARP_WIFI |
BR_NEIGH_SUPPRESS)))) {
- if (!vid)
+ replied = true;
+ if (!memcmp(n->ha, sha, dev->addr_len))
+ replied = false;
+ else if (!vid)
br_arp_send(br, p, skb->dev, sip, tip,
sha, n->ha, sha, 0, 0);
else
@@ -212,7 +215,6 @@ void br_do_proxy_suppress_arp(struct sk_
sha, n->ha, sha,
skb->vlan_proto,
skb_vlan_tag_get(skb));
- replied = true;
}
/* If we have replied or as long as we know the