Protocols will notify when dhcpcd can exit (#536)

* Protocols will notify when dhcpcd can exit

DHCPv6 RELEASE requires the addresses to be dropped before
a RELEASE message is sent.
We now wait for an acknowledgement or a timeout before notifying
that DHCPv6 has stopped for the interface.

DHCPv4 RELEASE is the other way around, there is no acknowledgement.
So we wait for 1 second after sending the message before removing
the address and notifying DHCP has stopped for the interface.

If we are not releasing then we notify dhcpcd that the protocol has
stopped right away when we drop the lease.

dhcpcd will exit once there are no running protocols for the
interfaces.

Fixes #513.
Hopefully #535, #519 and #509 as well.

Co-authored-by: Sime Zupanovic (EXT) <[email protected]>

Author: rsmarples

hooks/dhcpcd-run-hooks.8.in

@@ -22,7 +22,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd October 11, 2024
+.Dd October 6, 2025
 .Dt DHCPCD-RUN-HOOKS 8
 .Os
 .Sh NAME
@@ -105,6 +105,8 @@ dhcpcd renewed its lease.
 dhcpcd has rebound to a new DHCP server.
 .It Dv REBOOT | Dv REBOOT6
 dhcpcd successfully requested a lease from a DHCP server.
+.It Dv RELEASE | Dv RELEASE6
+dhcpcd has released the lease.
 .It Dv DELEGATED6
 dhcpcd assigned a delegated prefix to the interface.
 .It Dv IPV4LL

src/dhcp.c

@@ -2866,6 +2866,51 @@ dhcp_reboot(struct interface *ifp)
 	send_request(ifp);
 }
 
+static void
+dhcp_deconfigure(void *arg)
+{
+	struct interface *ifp = arg;
+	struct dhcp_state *state = D_STATE(ifp);
+	struct if_options *ifo = ifp->options;
+	const char *reason;
+
+#ifdef AUTH
+	dhcp_auth_reset(&state->auth);
+#endif
+
+	if (state->state == DHS_RELEASE)
+		reason = "RELEASE";
+	else
+		reason = state->reason;
+	state->state = DHS_NONE;
+	free(state->offer);
+	state->offer = NULL;
+	state->offer_len = 0;
+	free(state->old);
+	state->old = state->new;
+	state->old_len = state->new_len;
+	state->new = NULL;
+	state->new_len = 0;
+	if (ifo->options & DHCPCD_CONFIGURE)
+		ipv4_applyaddr(ifp);
+	else {
+		state->addr = NULL;
+		state->added = 0;
+	}
+	script_runreason(ifp, reason);
+	free(state->old);
+	state->old = NULL;
+	state->old_len = 0;
+	state->lease.addr.s_addr = 0;
+	ifo->options &= ~(DHCPCD_CSR_WARNED | DHCPCD_ROUTER_HOST_ROUTE_WARNED);
+
+	if (ifo->options & DHCPCD_STOPPING) {
+		dhcp_free(ifp);
+		dhcpcd_dropped(ifp);
+	} else
+		dhcp_close(ifp);
+}
+
 void
 dhcp_drop(struct interface *ifp, const char *reason)
 {
@@ -2876,6 +2921,7 @@ dhcp_drop(struct interface *ifp, const char *reason)
 	 * but we do have a timeout, so punt it. */
 	if (state == NULL || state->state == DHS_NONE) {
 		eloop_timeout_delete(ifp->ctx->eloop, NULL, ifp);
+		dhcpcd_dropped(ifp);
 		return;
 	}
 
@@ -2886,6 +2932,7 @@ dhcp_drop(struct interface *ifp, const char *reason)
 #ifdef ARPING
 	state->arping_index = -1;
 #endif
+	state->reason = reason;
 
 	if (ifo->options & DHCPCD_RELEASE && !(ifo->options & DHCPCD_INFORM)) {
 		/* Failure to send the release may cause this function to
@@ -2899,10 +2946,21 @@ dhcp_drop(struct interface *ifp, const char *reason)
 		    state->new != NULL &&
 		    state->lease.server.s_addr != INADDR_ANY)
 		{
+			/* We need to delay removal of the IP address so the
+			 * message can be sent.
+			 * Unlike DHCPv6, there is no acknowledgement. */
+			const struct timespec delay = {
+				.tv_sec = 1,
+			};
+
 			loginfox("%s: releasing lease of %s",
 			    ifp->name, inet_ntoa(state->lease.addr));
 			dhcp_new_xid(ifp);
 			send_message(ifp, DHCP_RELEASE, NULL);
+			eloop_timeout_delete(ifp->ctx->eloop, NULL, ifp);
+			eloop_timeout_add_tv(ifp->ctx->eloop,
+			    &delay, dhcp_deconfigure, ifp);
+			return;
 		}
 	}
 #ifdef AUTH
@@ -2919,36 +2977,7 @@ dhcp_drop(struct interface *ifp, const char *reason)
 #endif
 
 	eloop_timeout_delete(ifp->ctx->eloop, NULL, ifp);
-#ifdef AUTH
-	dhcp_auth_reset(&state->auth);
-#endif
-
-	state->state = DHS_NONE;
-	free(state->offer);
-	state->offer = NULL;
-	state->offer_len = 0;
-	free(state->old);
-	state->old = state->new;
-	state->old_len = state->new_len;
-	state->new = NULL;
-	state->new_len = 0;
-	state->reason = reason;
-	if (ifo->options & DHCPCD_CONFIGURE)
-		ipv4_applyaddr(ifp);
-	else {
-		state->addr = NULL;
-		state->added = 0;
-		script_runreason(ifp, state->reason);
-	}
-	free(state->old);
-	state->old = NULL;
-	state->old_len = 0;
-	state->lease.addr.s_addr = 0;
-	ifo->options &= ~(DHCPCD_CSR_WARNED | DHCPCD_ROUTER_HOST_ROUTE_WARNED);
-
-	/* Close DHCP ports so a changed interface family is picked
-	 * up by a new BPF state. */
-	dhcp_close(ifp);
+	dhcp_deconfigure(ifp);
 }
 
 static int
@@ -3108,6 +3137,12 @@ dhcp_handledhcp(struct interface *ifp, struct bootp *bootp, size_t bootp_len,
 #define IS_STATE_ACTIVE(s) ((s)-state != DHS_NONE && \
 	(s)->state != DHS_INIT && (s)->state != DHS_BOUND)
 
+	/* Don't do anything if the user hasn't configured it. */
+	if (ifp->active != IF_ACTIVE_USER ||
+	    ifp->options->options & DHCPCD_STOPPING ||
+	    !(ifp->options->options & DHCPCD_DHCP))
+		return;
+
 	if (bootp->op != BOOTREPLY) {
 		if (IS_STATE_ACTIVE(state))
 			logdebugx("%s: op (%d) is not BOOTREPLY",
@@ -3932,6 +3967,7 @@ dhcp_free(struct interface *ifp)
 		free(state->offer);
 		free(state->clientid);
 		free(state);
+		ifp->if_data[IF_DATA_DHCP] = NULL;
 	}
 
 	ctx = ifp->ctx;

src/dhcp6.c

@@ -2110,29 +2110,25 @@ dhcp6_startrelease(struct interface *ifp)
 	struct dhcp6_state *state;
 
 	state = D6_STATE(ifp);
-	if (state->state != DH6S_BOUND)
+	if (state->state != DH6S_BOUND) {
+		dhcp6_finishrelease(ifp);
 		return;
+	}
 
 	state->state = DH6S_RELEASE;
 	state->RTC = 0;
 	state->IMD = REL_MAX_DELAY;
 	state->IRT = REL_TIMEOUT;
 	state->MRT = REL_MAX_RT;
-	/* MRC of REL_MAX_RC is optional in RFC 3315 18.1.6 */
-#if 0
 	state->MRC = REL_MAX_RC;
 	state->MRCcallback = dhcp6_finishrelease;
-#else
-	state->MRC = 0;
-	state->MRCcallback = NULL;
-#endif
 
-	if (dhcp6_makemessage(ifp) == -1)
+	if (dhcp6_makemessage(ifp) == -1) {
 		logerr("%s: %s", __func__, ifp->name);
-	else {
-		dhcp6_sendrelease(ifp);
+		/* not much we can do apart from finish now */
 		dhcp6_finishrelease(ifp);
-	}
+	} else
+		dhcp6_sendrelease(ifp);
 }
 
 static int
@@ -3610,6 +3606,11 @@ dhcp6_recvif(struct interface *ifp, const char *sfrom,
 			    ifp->name, sfrom);
 			dhcp6_fail(ifp, true);
 			return;
+		case DH6S_RELEASE:
+			loginfox("%s: %s acknowledged RELEASE6",
+			    ifp->name, sfrom);
+			dhcp6_finishrelease(ifp);
+			return;
 		default:
 			valid_op = false;
 			break;
@@ -4293,6 +4294,7 @@ dhcp6_freedrop(struct interface *ifp, int drop, const char *reason)
 		free(state);
 		ifp->if_data[IF_DATA_DHCP6] = NULL;
 	}
+	dhcpcd_dropped(ifp);
 
 	/* If we don't have any more DHCP6 enabled interfaces,
 	 * close the global socket and release resources */