DHCP: Don't listen on the unspecified address when not in master mode

Otherwise we will swallow messages for another interface.
If we fail to bind to the address:BOOTPC socket then re-open
BPF. This could be due to address sharing (which isn't supported
withoutn master mode) or even worse another DHCP client running
on the same address. In this case, re-open BPF so we can listen
to RECONFIGURE messages.

diff --git a/src/dhcp.c b/src/dhcp.c
index 4ba4ebca566278af3b4cdc5304b747ebd53c9fdf..f5c5c094d2b7dbb035d7576652817dd310a3750f 100644 (file)
--- a/src/dhcp.c
+++ b/src/dhcp.c
@@ -2236,7 +2236,7 @@ dhcp_bind(struct interface *ifp)
        ipv4_applyaddr(ifp);
 
 #ifdef IP_PKTINFO
-       /* Close the BPF filter as we can now receive the DHCP renew messages
+       /* Close the BPF filter as we can now receive DHCP messages
         * on a UDP socket. */
        if (state->udp_fd == -1 ||
            (state->old != NULL && state->old->yiaddr != state->new->yiaddr))
@@ -2245,9 +2245,15 @@ dhcp_bind(struct interface *ifp)
                /* If not in master mode, open an address specific socket. */
                if (ctx->udp_fd == -1) {
                        state->udp_fd = dhcp_openudp(ifp);
-                       if (state->udp_fd == -1)
+                       if (state->udp_fd == -1) {
                                logerr(__func__);
-                       else
+                               /* Address sharing without master mode is
+                                * not supported. It's also possible another
+                                * DHCP client could be running which is
+                                * even worse.
+                                * We still need to work, so re-open BPF. */
+                               dhcp_openbpf(ifp);
+                       } else
                                eloop_event_add(ctx->eloop,
                                    state->udp_fd, dhcp_handleifudp, ifp);
                }
@@ -3662,6 +3668,7 @@ static void
 dhcp_start1(void *arg)
 {
        struct interface *ifp = arg;
+       struct dhcpcd_ctx *ctx = ifp->ctx;
        struct if_options *ifo = ifp->options;
        struct dhcp_state *state;
        struct stat st;
@@ -3672,17 +3679,19 @@ dhcp_start1(void *arg)
                return;
 
        /* Listen on *.*.*.*:bootpc so that the kernel never sends an
-        * ICMP port unreachable message back to the DHCP server */
-       if (ifp->ctx->udp_fd == -1) {
-               ifp->ctx->udp_fd = dhcp_openudp(NULL);
-               if (ifp->ctx->udp_fd == -1) {
+        * ICMP port unreachable message back to the DHCP server.
+        * Only do this in master mode so we don't swallow messages
+        * for dhcpcd running on another interface. */
+       if (ctx->udp_fd == -1 && ctx->options & DHCPCD_MASTER) {
+               ctx->udp_fd = dhcp_openudp(NULL);
+               if (ctx->udp_fd == -1) {
                        /* Don't log an error if some other process
                         * is handling this. */
                        if (errno != EADDRINUSE)
                                logerr("%s: dhcp_openudp", __func__);
                } else
-                       eloop_event_add(ifp->ctx->eloop,
-                           ifp->ctx->udp_fd, dhcp_handleudp, ifp->ctx);
+                       eloop_event_add(ctx->eloop,
+                           ctx->udp_fd, dhcp_handleudp, ctx);
        }
 
        if (dhcp_init(ifp) == -1) {