From 1d957df5cc0b9583af98d469f9aa1738a7e9c536 Mon Sep 17 00:00:00 2001
From: Roy Marples <roy@marples.name>
Date: Sun, 14 Aug 2016 08:51:19 +0000
Subject: [PATCH] Bind to the local-link address rather than directly to the
 interface to allow many DHCPv6 clients on many interfaces. This works on all
 platforms.

---
 dhcp6.c | 27 ++++++++++-----------------
 1 file changed, 10 insertions(+), 17 deletions(-)

diff --git a/dhcp6.c b/dhcp6.c
index 45fd5e3f..27aac291 100644
--- a/dhcp6.c
+++ b/dhcp6.c
@@ -3174,28 +3174,21 @@ dhcp6_open(struct dhcpcd_ctx *dctx)
 		logger(dctx, LOG_WARNING, "setsockopt: SO_REUSEPORT: %m");
 #endif
 
-#ifdef SO_BINDTODEVICE
-	/* If we're not running in master mode, we can bind directly to the
-	 * interface. This allows separate daemons to work on separate
-	 * interfaces. */
 	if (!(dctx->options & DHCPCD_MASTER)) {
-		const struct interface *ifp;
-		struct ifreq ifr;
+		/* Bind to the link-local address to allow more than one
+		 * DHCPv6 client to work. */
+		struct interface *ifp;
+		struct ipv6_addr *ia;
 
 		TAILQ_FOREACH(ifp, dctx->ifaces, next) {
 			if (ifp->active)
 				break;
 		}
-		if (ifp != NULL) {
-			memset(&ifr, 0, sizeof(ifr));
-			strlcpy(ifr.ifr_name, ifp->name, sizeof(ifr.ifr_name));
-			if (setsockopt(ctx->dhcp_fd, SOL_SOCKET, SO_BINDTODEVICE, &ifr,
-			    sizeof(ifr)) == -1)
-				logger(dctx, LOG_WARNING,
-				    "setsockopt: SO_BINDTODEVICE: %m");
+		if ((ia = ipv6_linklocal(ifp)) != NULL) {
+			memcpy(&sa.sin6_addr, &ia->addr, sizeof(sa.sin6_addr));
+			sa.sin6_scope_id = ifp->index;
 		}
 	}
-#endif
 
 	if (bind(ctx->dhcp_fd, (struct sockaddr *)&sa, sizeof(sa)) == -1)
 		goto errexit;
@@ -3253,6 +3246,9 @@ dhcp6_start1(void *arg)
 	size_t i;
 	const struct dhcp_compat *dhc;
 
+	if (ifp->ctx->ipv6->dhcp_fd == -1 && dhcp6_open(ifp->ctx) == -1)
+		return;
+
 	state = D6_STATE(ifp);
 	/* If no DHCPv6 options are configured,
 	   match configured DHCPv4 options to DHCPv6 equivalents. */
@@ -3317,9 +3313,6 @@ dhcp6_start(struct interface *ifp, enum DH6S init_state)
 	if (!(ifp->options->options & DHCPCD_DHCP6))
 		return 0;
 
-	if (ifp->ctx->ipv6->dhcp_fd == -1 && dhcp6_open(ifp->ctx) == -1)
-		return -1;
-
 	ifp->if_data[IF_DATA_DHCP6] = calloc(1, sizeof(*state));
 	state = D6_STATE(ifp);
 	if (state == NULL)
-- 
2.47.3