BSD: struct if_data->ifi_link_state is the single source of truth

Vastly improve and simplify link detection on BSD.
dhcpcd either examines the whole system via getifaddrs(3) or
reacts to events via route(4).
In both cases we have struct if_data which has ifi_link_state.

Armed with this knowledge, we no longer need SIOCGIFDATA or
SIOCGIFMEDIA.

To solve the issue of newly attached interfaces having
LINK_STATE_UNKNOWN or some interfaces not even changing it,
we only change the local knowledge of interface flags when
reports them by getifaddrs(3) or route(4) when we change them.
For example, if we set IFF_UP and it succeeds we don't set this
internally until reported by the kernel as above.

This keeps flags and link state in sync with each other.
The hope is that the kernel can set the real link state before
it reports IFF_UP.

As such, we no longer require the poll option or need to enter a
tight loop for old interfaces.

1 files changed, 28 insertions, 52 deletions

diff --git a/src/dhcpcd.c b/src/dhcpcd.c
index e193b6ee..1fd0ae18 100644
--- a/src/dhcpcd.c
+++ b/src/dhcpcd.c
@@ -432,8 +432,6 @@ stop_interface(struct interface *ifp)
 	/* De-activate the interface */
 	ifp->active = IF_INACTIVE;
 	ifp->options->options &= ~DHCPCD_STOPPING;
-	/* Set the link state to unknown as we're no longer tracking it. */
-	ifp->carrier = LINK_UNKNOWN;
 
 	if (!(ctx->options & (DHCPCD_MASTER | DHCPCD_TEST)))
 		eloop_exit(ctx->eloop, EXIT_FAILURE);
@@ -704,42 +702,32 @@ dhcpcd_reportssid(struct interface *ifp)
 }
 
 void
-dhcpcd_handlecarrier(struct dhcpcd_ctx *ctx, int carrier, unsigned int flags,
-    const char *ifname)
+dhcpcd_handlecarrier(struct interface *ifp, int carrier, unsigned int flags)
 {
-	struct interface *ifp;
-
-	ifp = if_find(ctx->ifaces, ifname);
-	if (ifp == NULL ||
-	    ifp->options == NULL || !(ifp->options->options & DHCPCD_LINK))
-		return;
+	bool nolink = ifp->options == NULL ||
+	    !(ifp->options->options & DHCPCD_LINK);
 
+	ifp->flags = flags;
 	if (carrier == LINK_UNKNOWN) {
-		if (ifp->wireless) {
+		if (ifp->wireless)
 			carrier = LINK_DOWN;
-			ifp->flags = flags;
-		} else
-			carrier = if_carrier(ifp);
-	} else
-		ifp->flags = flags;
-	if (carrier == LINK_UNKNOWN)
-		carrier = IF_UPANDRUNNING(ifp) ? LINK_UP : LINK_DOWN;
+		else
+			carrier = IF_UPANDRUNNING(ifp) ? LINK_UP : LINK_DOWN;
+	}
 
 	if (carrier == LINK_DOWN || (ifp->flags & IFF_UP) == 0) {
 		if (ifp->carrier != LINK_DOWN) {
-			int oldcarrier = ifp->carrier;
-
 #ifdef NOCARRIER_PRESERVE_IP
 			if (ifp->flags & IFF_UP &&
-			    !(ifp->options->options & DHCPCD_ANONYMOUS))
+			    (ifp->options == NULL ||
+			    !(ifp->options->options & DHCPCD_ANONYMOUS)))
 				ifp->carrier = LINK_DOWN_IFFUP;
 			else
 #endif
 				ifp->carrier = LINK_DOWN;
-			if (!ifp->active)
+			if (!ifp->active || nolink)
 				return;
-			if (oldcarrier == LINK_UP)
-				loginfox("%s: carrier lost", ifp->name);
+			loginfox("%s: carrier lost", ifp->name);
 			script_runreason(ifp, "NOCARRIER");
 #ifdef NOCARRIER_PRESERVE_IP
 			if (ifp->flags & IFF_UP &&
@@ -801,7 +789,7 @@ dhcpcd_handlecarrier(struct dhcpcd_ctx *ctx, int carrier, unsigned int flags,
 #endif
 				}
 			}
-			if (!ifp->active)
+			if (!ifp->active || nolink)
 				return;
 			dhcpcd_initstate(ifp, 0);
 			script_runreason(ifp, "CARRIER");
@@ -878,20 +866,11 @@ dhcpcd_startinterface(void *arg)
 	struct interface *ifp = arg;
 	struct if_options *ifo = ifp->options;
 
-	if (ifo->options & DHCPCD_LINK) {
-		switch (ifp->carrier) {
-		case LINK_UP:
-			break;
-		case LINK_DOWN:
-			loginfox("%s: waiting for carrier", ifp->name);
-			return;
-		case LINK_UNKNOWN:
-			/* No media state available.
-			 * Loop until both IFF_UP and IFF_RUNNING are set */
-			if (ifo->poll == 0)
-				if_pollinit(ifp);
-			return;
-		}
+	if (ifo->options & DHCPCD_LINK && (ifp->carrier == LINK_DOWN ||
+	    (ifp->carrier == LINK_UNKNOWN && !IF_UPANDRUNNING(ifp))))
+	{
+		loginfox("%s: waiting for carrier", ifp->name);
+		return;
 	}
 
 	if (ifo->options & (DHCPCD_DUID | DHCPCD_IPV6) &&
@@ -1000,9 +979,6 @@ dhcpcd_prestartinterface(void *arg)
 			logerr(__func__);
 	}
 
-	if (ifp->options->poll != 0)
-		if_pollinit(ifp);
-
 	dhcpcd_startinterface(ifp);
 }
 
@@ -1138,14 +1114,14 @@ dhcpcd_handlelink(void *arg)
 static void
 dhcpcd_checkcarrier(void *arg)
 {
-	struct interface *ifp = arg;
-	int carrier;
+	struct interface *ifp0 = arg, *ifp;
 
-	/* Check carrier here rather than setting LINK_UNKNOWN.
-	 * This is because we force LINK_UNKNOWN as down for wireless which
-	 * we do not want when dealing with a route socket overflow. */
-	carrier = if_carrier(ifp);
-	dhcpcd_handlecarrier(ifp->ctx, carrier, ifp->flags, ifp->name);
+	ifp = if_find(ifp0->ctx->ifaces, ifp0->name);
+	if (ifp == NULL || ifp->carrier == ifp0->carrier)
+		return;
+
+	dhcpcd_handlecarrier(ifp, ifp0->carrier, ifp0->flags);
+	if_free(ifp0);
 }
 
 #ifndef SMALL
@@ -1231,10 +1207,10 @@ dhcpcd_linkoverflow(struct dhcpcd_ctx *ctx)
 		ifp1 = if_find(ctx->ifaces, ifp->name);
 		if (ifp1 != NULL) {
 			/* If the interface already exists,
-			 * check carrier state. */
+			 * check carrier state.
+			 * dhcpcd_checkcarrier will free ifp. */
 			eloop_timeout_add_sec(ctx->eloop, 0,
-			    dhcpcd_checkcarrier, ifp1);
-			if_free(ifp);
+			    dhcpcd_checkcarrier, ifp);
 			continue;
 		}
 		TAILQ_INSERT_TAIL(ctx->ifaces, ifp, next);