batman-adv: send every DHCP packet as bat-unicast

In different situations it is possible that the DHCP server
or client uses broadcast Ethernet frames to send messages
to each other. The GW component in batman-adv takes care of
using bat-unicast packets to bring broadcast DHCP
Discover/Requests to the "best" server.

On the way back the DHCP server usually sends unicasts,
but upon client request it may decide to use broadcasts as
well.

This patch improves the GW component so that it now snoops
and sends as unicast all the DHCP packets, no matter if they
were generated by a DHCP server or client.

Signed-off-by: Antonio Quartulli <antonio@open-mesh.com>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>

1 files changed, 41 insertions, 35 deletions

diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index 3686be7805f3..b569932ddcc4 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -160,6 +160,8 @@ static int batadv_interface_tx(struct sk_buff *skb,
 						   0x00, 0x00};
 	static const uint8_t ectp_addr[ETH_ALEN] = {0xCF, 0x00, 0x00, 0x00,
 						    0x00, 0x00};
+	enum batadv_dhcp_recipient dhcp_rcp = BATADV_DHCP_NO;
+	uint8_t *dst_hint = NULL, chaddr[ETH_ALEN];
 	struct vlan_ethhdr *vhdr;
 	unsigned int header_len = 0;
 	int data_len = skb->len, ret;
@@ -167,6 +169,7 @@ static int batadv_interface_tx(struct sk_buff *skb,
 	bool do_bcast = false, client_added;
 	unsigned short vid;
 	uint32_t seqno;
+	int gw_mode;
 
 	if (atomic_read(&bat_priv->mesh_state) != BATADV_MESH_ACTIVE)
 		goto dropped;
@@ -213,36 +216,39 @@ static int batadv_interface_tx(struct sk_buff *skb,
 	if (batadv_compare_eth(ethhdr->h_dest, ectp_addr))
 		goto dropped;
 
+	gw_mode = atomic_read(&bat_priv->gw_mode);
 	if (is_multicast_ether_addr(ethhdr->h_dest)) {
-		do_bcast = true;
-
-		switch (atomic_read(&bat_priv->gw_mode)) {
-		case BATADV_GW_MODE_SERVER:
-			/* gateway servers should not send dhcp
-			 * requests into the mesh
-			 */
-			ret = batadv_gw_is_dhcp_target(skb, &header_len);
-			if (ret)
-				goto dropped;
-			break;
-		case BATADV_GW_MODE_CLIENT:
-			/* gateway clients should send dhcp requests
-			 * via unicast to their gateway
-			 */
-			ret = batadv_gw_is_dhcp_target(skb, &header_len);
-			if (ret)
-				do_bcast = false;
-			break;
-		case BATADV_GW_MODE_OFF:
-		default:
-			break;
+		/* if gw mode is off, broadcast every packet */
+		if (gw_mode == BATADV_GW_MODE_OFF) {
+			do_bcast = true;
+			goto send;
 		}
 
-		/* reminder: ethhdr might have become unusable from here on
-		 * (batadv_gw_is_dhcp_target() might have reallocated skb data)
+		dhcp_rcp = batadv_gw_dhcp_recipient_get(skb, &header_len,
+							chaddr);
+		/* skb->data may have been modified by
+		 * batadv_gw_dhcp_recipient_get()
 		 */
+		ethhdr = (struct ethhdr *)skb->data;
+		/* if gw_mode is on, broadcast any non-DHCP message.
+		 * All the DHCP packets are going to be sent as unicast
+		 */
+		if (dhcp_rcp == BATADV_DHCP_NO) {
+			do_bcast = true;
+			goto send;
+		}
+
+		if (dhcp_rcp == BATADV_DHCP_TO_CLIENT)
+			dst_hint = chaddr;
+		else if ((gw_mode == BATADV_GW_MODE_SERVER) &&
+			 (dhcp_rcp == BATADV_DHCP_TO_SERVER))
+			/* gateways should not forward any DHCP message if
+			 * directed to a DHCP server
+			 */
+			goto dropped;
 	}
 
+send:
 	batadv_skb_set_priority(skb, 0);
 
 	/* ethernet packet should be broadcasted */
@@ -288,22 +294,22 @@ static int batadv_interface_tx(struct sk_buff *skb,
 
 	/* unicast packet */
 	} else {
-		if (atomic_read(&bat_priv->gw_mode) != BATADV_GW_MODE_OFF) {
+		/* DHCP packets going to a server will use the GW feature */
+		if (dhcp_rcp == BATADV_DHCP_TO_SERVER) {
 			ret = batadv_gw_out_of_range(bat_priv, skb);
 			if (ret)
 				goto dropped;
-		}
-
-		if (batadv_dat_snoop_outgoing_arp_request(bat_priv, skb))
-			goto dropped;
-
-		batadv_dat_snoop_outgoing_arp_reply(bat_priv, skb);
-
-		if (is_multicast_ether_addr(ethhdr->h_dest))
 			ret = batadv_send_skb_via_gw(bat_priv, skb, vid);
-		else
-			ret = batadv_send_skb_via_tt(bat_priv, skb, vid);
+		} else {
+			if (batadv_dat_snoop_outgoing_arp_request(bat_priv,
+								  skb))
+				goto dropped;
 
+			batadv_dat_snoop_outgoing_arp_reply(bat_priv, skb);
+
+			ret = batadv_send_skb_via_tt(bat_priv, skb, dst_hint,
+						     vid);
+		}
 		if (ret == NET_XMIT_DROP)
 			goto dropped_freed;
 	}