ndp: Allow NS loopback for master iface

This commit modifies handle_solicit() in ndp.c to correct IPv6 relay
handling of Neighbor Solicitation (NS) requests when no upstream
solicitation is received.

Background: In IPv6 relay mode, odhcpd discovers local devices only upon
receiving upstream NS packets. If no upstream NS arrives (e.g. because the
upstream router’s neighbor cache is still valid or no solicitation was
ever sent), OpenWrt may attempt neighbor resolution via the master (WAN)
interface instead of the LAN, leaving local devices undiscoverable and
breaking connectivity.

- When an NS packet is sent by the host's master interface, do not
  immediately return; instead continue searching slave interfaces for the
  target neighbor.
- When odhcpd responds to NS packets, add a check to prevent replying to
  NS packets that were sent by the host itself.

Signed-off-by: Haoyi Ci [email protected]
Link: https://github.com/openwrt/odhcpd/pull/240
Signed-off-by: Álvaro Fernández Rojas <[email protected]>

diff --git a/src/ndp.c b/src/ndp.c
index 0ec6fed5ff37ebb6446f5a2468226cf0d11cc7ec..0feb8145ed69148981d5994a0affbd4b22eedc93 100644 (file)
--- a/src/ndp.c
+++ b/src/ndp.c
@@ -332,6 +332,7 @@ static void handle_solicit(void *addr, void *data, size_t len,
        struct interface *c;
        char ipbuf[INET6_ADDRSTRLEN];
        uint8_t mac[6];
+       bool is_self_sent;
 
        /* Solicitation is for duplicate address detection */
        bool ns_is_dad = IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src);
@@ -354,7 +355,8 @@ static void handle_solicit(void *addr, void *data, size_t len,
        syslog(LOG_DEBUG, "Got a NS for %s on %s", ipbuf, iface->name);
 
        odhcpd_get_mac(iface, mac);
-       if (!memcmp(ll->sll_addr, mac, sizeof(mac)))
+       is_self_sent = !memcmp(ll->sll_addr, mac, sizeof(mac));
+       if (is_self_sent && !iface->master)
                return; /* Looped back */
 
        avl_for_each_element(&interfaces, c, avl) {
@@ -366,7 +368,7 @@ static void handle_solicit(void *addr, void *data, size_t len,
        /* Catch global-addressed NS and answer them manually.
         * The kernel won't answer these and cannot route them either. */
        if (!IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) &&
-                       IN6_IS_ADDR_LINKLOCAL(&ip6->ip6_src)) {
+                       IN6_IS_ADDR_LINKLOCAL(&ip6->ip6_src) && !is_self_sent) {
                bool is_proxy_neigh = netlink_get_interface_proxy_neigh(iface->ifindex,
                                &req->nd_ns_target) == 1;