kernel-pfroute: Improve route lookup depending on information we get back

Kernels don't provide the same information for all routes.

src/libhydra/plugins/kernel_pfroute/kernel_pfroute_net.c

@@ -1086,6 +1086,48 @@ METHOD(kernel_net_t, del_route, status_t,
 	return manage_route(this, RTM_DELETE, dst_net, prefixlen, gateway, if_name);
 }
 
+/**
+ * Get an address on the given interface, preferably src.
+ */
+static host_t *get_address_on(private_kernel_pfroute_net_t *this, char *ifname,
+                             host_t *src)
+{
+	enumerator_t *ifaces, *addrs;
+	iface_entry_t *iface;
+	addr_entry_t *addr, *found = NULL;
+	host_t *host = NULL;
+
+	this->lock->read_lock(this->lock);
+	ifaces = this->ifaces->create_enumerator(this->ifaces);
+	while (ifaces->enumerate(ifaces, &iface))
+	{
+		if (streq(ifname, iface->ifname))
+		{
+			addrs = iface->addrs->create_enumerator(iface->addrs);
+			while (addrs->enumerate(addrs, &addr))
+			{
+				if (src->ip_equals(src, addr->ip))
+				{
+					found = addr;
+					break;
+				}
+				else if (!found)
+				{   /* use the first address as fallback if we don't find src */
+					found = addr;
+				}
+			}
+			addrs->destroy(addrs);
+			if (found)
+			{
+				host = found->ip->clone(found->ip);
+			}
+			break;
+		}
+	}
+	ifaces->destroy(ifaces);
+	this->lock->unlock(this->lock);
+	return host;
+}
 /**
  * Do a route lookup for dest and return either the nexthop or the source
  * address.
@@ -1104,9 +1146,10 @@ static host_t *get_route(private_kernel_pfroute_net_t *this, bool nexthop,
 			.rtm_seq = ++this->seq,
 		},
 	};
-	host_t *host = NULL;
+	host_t *host = NULL, *gtw = NULL, *dst = NULL, *ifa = NULL;
 	enumerator_t *enumerator;
 	struct sockaddr *addr;
+	char *ifname = NULL;
 	int type;
 
 	msg.hdr.rtm_msglen = sizeof(struct rt_msghdr);
@@ -1154,21 +1197,25 @@ static host_t *get_route(private_kernel_pfroute_net_t *this, bool nexthop,
 												 sizeof(*this->reply));
 			while (enumerator->enumerate(enumerator, &type, &addr))
 			{
-				if (nexthop && type == RTAX_GATEWAY)
+				if (type == RTAX_DST && this->reply->rtm_flags & RTF_HOST)
-				{
+				{	/* probably a cloned/cached direct route */
-					host = host_create_from_sockaddr(addr);
+					dst = host_create_from_sockaddr(addr);
-					break;
 				}
-				if (nexthop && type == RTAX_DST &&
+				if (type == RTAX_GATEWAY)
-					this->reply->rtm_flags & RTF_HOST)
-				{	/* probably a cloned direct route */
-					host = host_create_from_sockaddr(addr);
-					break;
-				}
-				if (!nexthop && type == RTAX_IFA)
 				{
-					host = host_create_from_sockaddr(addr);
+					gtw = host_create_from_sockaddr(addr);
-					break;
+				}
+				if (type == RTAX_IFA)
+				{
+					ifa = host_create_from_sockaddr(addr);
+				}
+				if (type == RTAX_IFP)
+				{
+					struct sockaddr_dl *sdl = (struct sockaddr_dl*)addr;
+					if (addr->sa_family == AF_LINK && sdl->sdl_nlen)
+					{
+						ifname = strndup(sdl->sdl_data, sdl->sdl_nlen);
+					}
 				}
 			}
 			enumerator->destroy(enumerator);
@@ -1184,6 +1231,43 @@ static host_t *get_route(private_kernel_pfroute_net_t *this, bool nexthop,
 	this->condvar->signal(this->condvar);
 	this->mutex->unlock(this->mutex);
 
+	DBG3(DBG_KNL, "route to %H: dst %H gw %H src %H if %s", dest, dst, gtw,
+		 ifa, ifname);
+	if (nexthop)
+	{
+		if (gtw)
+		{
+			host = gtw->clone(gtw);
+		}
+		else if (dst)
+		{
+			host = dst->clone(dst);
+		}
+	}
+	else
+	{
+		if (ifa)
+		{
+			host = ifa->clone(ifa);
+		}
+		else if (ifname)
+		{
+			host = get_address_on(this, ifname, src);
+		}
+		else if (gtw && !gtw->ip_equals(gtw, dest))
+		{
+			host = get_route(this, FALSE, gtw, src);
+		}
+	}
+	if (host)
+	{
+		DBG2(DBG_KNL, "using %H as %s to reach %H", host,
+			 nexthop ? "nexthop" : "address", dest);
+	}
+	DESTROY_IF(gtw);
+	DESTROY_IF(dst);
+	DESTROY_IF(ifa);
+	free(ifname);
 	return host;
 }