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, 14 insertions, 91 deletions

diff --git a/src/if-bsd.c b/src/if-bsd.c
index bdcd2901..3eb78045 100644
--- a/src/if-bsd.c
+++ b/src/if-bsd.c
@@ -377,84 +377,23 @@ static int if_indirect_ioctl(struct dhcpcd_ctx *ctx,
 	return ioctl(ctx->pf_inet_fd, cmd, &ifr);
 }
 
-static int
-if_carrier0(struct interface *ifp)
-{
-	struct ifmediareq ifmr = { .ifm_status = 0 };
-
-	/* Not really needed, but the other OS update flags here also */
-	if (if_getflags(ifp) == -1)
-		return LINK_UNKNOWN;
-
-	strlcpy(ifmr.ifm_name, ifp->name, sizeof(ifmr.ifm_name));
-	if (ioctl(ifp->ctx->pf_inet_fd, SIOCGIFMEDIA, &ifmr) == -1)
-		return LINK_UNKNOWN;
-
-	if (!(ifmr.ifm_status & IFM_AVALID))
-		return LINK_UNKNOWN;
-
-	return (ifmr.ifm_status & IFM_ACTIVE) ? LINK_UP : LINK_DOWN;
-}
-
 int
-if_carrier(struct interface *ifp)
+if_carrier(__unused struct interface *ifp, const void *ifadata)
 {
-	int carrier = if_carrier0(ifp);
+	const struct if_data *ifi = ifadata;
 
-#ifdef SIOCGIFDATA
-	if (carrier != LINK_UNKNOWN)
-		return carrier;
-
-#ifdef __NetBSD__
-	struct ifdatareq ifdr = { .ifdr_data.ifi_link_state = 0 };
-	struct if_data *ifdata = &ifdr.ifdr_data;
-
-	strlcpy(ifdr.ifdr_name, ifp->name, sizeof(ifdr.ifdr_name));
-	if (ioctl(ifp->ctx->pf_inet_fd, SIOCGIFDATA, &ifdr) == -1)
-		return LINK_UNKNOWN;
-#else
-	struct if_data ifd = { .ifi_link_state = 0 };
-	struct if_data *ifdata = &ifd;
-
-	if (if_indirect_ioctl(ifp->ctx, ifp->name, SIOCGIFDATA,
-	    &ifd, sizeof(ifd)) == -1)
-		return LINK_UNKNOWN;
-#endif
-
-	switch (ifdata->ifi_link_state) {
-	case LINK_STATE_DOWN:
-		return LINK_DOWN;
-#ifdef LINK_STATE_HALF_DUPLEX
-	case LINK_STATE_HALF_DUPLEX:
-	case LINK_STATE_FULL_DUPLEX:
-#endif
-	case LINK_STATE_UP:
-		return LINK_UP;
-	}
-	return LINK_UNKNOWN;
-#else
-#warning no SIOCGIFDATA - not all interfaces support SIOCGIFMEDIA
-	return carrier;
-#endif
-}
-
-int
-if_carrier_ifadata(struct interface *ifp, void *ifadata)
-{
-	int carrier = if_carrier0(ifp);
-	struct if_data *ifdata;
-
-	if (carrier != LINK_UNKNOWN || ifadata == NULL)
-		return carrier;
+	/*
+	 * Every BSD returns this and it is the sole source of truth.
+	 * Not all BSD's support SIOCGIFDATA and not all interfaces
+	 * support SIOCGIFMEDIA.
+	 */
+	assert(ifadata != NULL);
 
-	ifdata = ifadata;
-	switch (ifdata->ifi_link_state) {
-	case LINK_STATE_DOWN:
-		return LINK_DOWN;
-	case LINK_STATE_UP:
+	if (ifi->ifi_link_state >= LINK_STATE_UP)
 		return LINK_UP;
-	}
-	return LINK_UNKNOWN;
+	if (ifi->ifi_link_state == LINK_STATE_UNKNOWN)
+		return LINK_UNKNOWN;
+	return LINK_DOWN;
 }
 
 static void
@@ -1254,24 +1193,8 @@ if_ifinfo(struct dhcpcd_ctx *ctx, const struct if_msghdr *ifm)
 	if ((ifp = if_findindex(ctx->ifaces, ifm->ifm_index)) == NULL)
 		return 0;
 
-	switch (ifm->ifm_data.ifi_link_state) {
-	case LINK_STATE_UNKNOWN:
-		link_state = LINK_UNKNOWN;
-		break;
-#ifdef LINK_STATE_FULL_DUPLEX
-	case LINK_STATE_HALF_DUPLEX:	/* FALLTHROUGH */
-	case LINK_STATE_FULL_DUPLEX:	/* FALLTHROUGH */
-#endif
-	case LINK_STATE_UP:
-		link_state = LINK_UP;
-		break;
-	default:
-		link_state = LINK_DOWN;
-		break;
-	}
-
-	dhcpcd_handlecarrier(ctx, link_state,
-	    (unsigned int)ifm->ifm_flags, ifp->name);
+	link_state = if_carrier(ifp, &ifm->ifm_data);
+	dhcpcd_handlecarrier(ifp, link_state, (unsigned int)ifm->ifm_flags);
 	return 0;
 }