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{bp-19872} net/arp: fix cross-interface resolution and a device-lock leak #20070

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Merged
xiaoxiang781216 merged 2 commits into from
Sep 7, 2026
Merged

{bp-19872} net/arp: fix cross-interface resolution and a device-lock leak #20070

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c55d96b
net/arp: release the device lock before waiting for a resolution
FelipeMdeO Aug 16, 2026
44a62a9
net/arp: do not resolve an address to another interface's MAC
FelipeMdeO Aug 16, 2026
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5 changes: 5 additions & 0 deletions net/arp/arp_send.c
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Original file line number Diff line number Diff line change
Expand Up @@ -328,8 +328,13 @@ int arp_send(in_addr_t ipaddr)
{
/* ARP request for the same destination is in progress, directly
* wait arp response notify.
*
* Drop the device lock: this path skips the netdev_unlock()
* below, and the receive path needs that same lock to deliver
* the reply. The waiter above is already installed.
*/

netdev_unlock(dev);
goto wait;
}

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16 changes: 14 additions & 2 deletions net/arp/arp_table.c
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Original file line number Diff line number Diff line change
Expand Up @@ -81,8 +81,9 @@

struct arp_table_info_s
{
in_addr_t ai_ipaddr; /* IP address for lookup */
FAR uint8_t *ai_ethaddr; /* Location to return the MAC address */
in_addr_t ai_ipaddr; /* IP address for lookup */
FAR uint8_t *ai_ethaddr; /* Location to return the MAC address */
FAR struct net_driver_s *ai_dev; /* The device the frame will be sent on */
};

/****************************************************************************
Expand Down Expand Up @@ -117,6 +118,16 @@ static int arp_match(FAR struct net_driver_s *dev, FAR void *arg)
{
FAR struct arp_table_info_s *info = arg;

/* Only the egress device may answer for its own address. Otherwise a
* frame sent on one interface takes the MAC of another that happens to
* hold the address, which breaks setups sharing a subnet.
*/

if (info->ai_dev != NULL && dev != info->ai_dev)
{
return 0;
}

/* Make sure that this is an Ethernet device (or an IEEE 802.11 device
* which is also Ethernet)
*/
Expand Down Expand Up @@ -529,6 +540,7 @@ int arp_find(in_addr_t ipaddr, FAR uint8_t *ethaddr,

info.ai_ipaddr = ipaddr;
info.ai_ethaddr = ethaddr;
info.ai_dev = dev;

if (netdev_foreach(arp_match, &info) != 0)
{
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