From: Paul Donald <newtwen+github@gmail.com>
Date: Mon, 17 Nov 2025 01:15:51 +0000 (+0100)
Subject: dhcpv6: prevent network loop scenario
X-Git-Url: http://git.openwrt.org/?a=commitdiff_plain;h=8c574bd2fe623cf8bb6e91f6f086e25a9f13e104;p=project%2Fodhcpd.git

dhcpv6: prevent network loop scenario

It's possible for odhcpd to talk with its (odhcp6c) self in a network loop
scenario with strange results. Prevent this by returning early.

Signed-off-by: Paul Donald <newtwen+github@gmail.com>
Link: https://github.com/openwrt/odhcpd/pull/314
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
---

diff --git a/src/dhcpv6.c b/src/dhcpv6.c
index a808400..9d81262 100644
--- a/src/dhcpv6.c
+++ b/src/dhcpv6.c
@@ -708,6 +708,12 @@ static void handle_client_request(void *addr, void *data, size_t len,
 		}
 	}
 
+	if (dest.serverid_length == clientid.len && 
+	    !memcmp(clientid.buf, dest.serverid_buf, dest.serverid_length)) {
+		/* Bail if we are in a network loop where we talk with ourself */
+		return;		
+	}
+
 	if (!IN6_IS_ADDR_MULTICAST((struct in6_addr *)dest_addr) && iov[IOV_NESTED].iov_len == 0 &&
 	    (hdr->msg_type == DHCPV6_MSG_REQUEST || hdr->msg_type == DHCPV6_MSG_RENEW ||
 	     hdr->msg_type == DHCPV6_MSG_RELEASE || hdr->msg_type == DHCPV6_MSG_DECLINE)) {