l2_packet: Allow initialization without RX handling

This can be used to minimize resource use when receive path is not
needed.

Signed-off-by: Jouni Malinen <j@w1.fi>

src/l2_packet/l2_packet.h

@@ -61,6 +61,10 @@ enum l2_packet_filter_type {
  * points to len bytes of the payload after the layer 2 header and similarly,
  * TX buffers start with payload. This behavior can be changed by setting
  * l2_hdr=1 to include the layer 2 header in the data buffer.
+ *
+ * IF rx_callback is NULL, receive operation is not opened at all, i.e., only
+ * the TX path and additional helper functions for fetching MAC and IP
+ * addresses can be used.
  */
 struct l2_packet_data * l2_packet_init(
 	const char *ifname, const u8 *own_addr, unsigned short protocol,

src/l2_packet/l2_packet_freebsd.c

@@ -84,7 +84,7 @@ static void l2_packet_receive(int sock, void *eloop_ctx, void *sock_ctx)
 
 	packet = pcap_next(pcap, &hdr);
 
-	if (packet == NULL || hdr.caplen < sizeof(*ethhdr))
+	if (!l2->rx_callback || !packet || hdr.caplen < sizeof(*ethhdr))
 		return;
 
 	ethhdr = (struct l2_ethhdr *) packet;

src/l2_packet/l2_packet_linux.c

@@ -312,7 +312,8 @@ struct l2_packet_data * l2_packet_init(
 	ll.sll_family = PF_PACKET;
 	ll.sll_ifindex = ifr.ifr_ifindex;
 	ll.sll_protocol = htons(protocol);
-	if (bind(l2->fd, (struct sockaddr *) &ll, sizeof(ll)) < 0) {
+	if (rx_callback &&
+	    bind(l2->fd, (struct sockaddr *) &ll, sizeof(ll)) < 0) {
 		wpa_printf(MSG_ERROR, "%s: bind[PF_PACKET]: %s",
 			   __func__, strerror(errno));
 		close(l2->fd);
@@ -329,7 +330,8 @@ struct l2_packet_data * l2_packet_init(
 	}
 	os_memcpy(l2->own_addr, ifr.ifr_hwaddr.sa_data, ETH_ALEN);
 
-	eloop_register_read_sock(l2->fd, l2_packet_receive, l2, NULL);
+	if (rx_callback)
+		eloop_register_read_sock(l2->fd, l2_packet_receive, l2, NULL);
 
 	return l2;
 }

src/l2_packet/l2_packet_ndis.c

@@ -294,7 +294,8 @@ static void l2_packet_callback(struct l2_packet_data *l2)
 	}
 	rx_src = ethhdr->h_source;
 
-	l2->rx_callback(l2->rx_callback_ctx, rx_src, rx_buf, rx_len);
+	if (l2->rx_callback)
+		l2->rx_callback(l2->rx_callback_ctx, rx_src, rx_buf, rx_len);
 #ifndef _WIN32_WCE
 	l2_ndisuio_start_read(l2, 1);
 #endif /* _WIN32_WCE */

src/l2_packet/l2_packet_none.c

@@ -84,7 +84,7 @@ struct l2_packet_data * l2_packet_init(
 	 * TODO: open connection for receiving frames
 	 */
 	l2->fd = -1;
-	if (l2->fd >= 0)
+	if (rx_callback && l2->fd >= 0)
 		eloop_register_read_sock(l2->fd, l2_packet_receive, l2, NULL);
 
 	return l2;

src/l2_packet/l2_packet_pcap.c

@@ -127,7 +127,7 @@ static void l2_packet_receive(int sock, void *eloop_ctx, void *sock_ctx)
 
 	packet = pcap_next(pcap, &hdr);
 
-	if (packet == NULL || hdr.caplen < sizeof(*ethhdr))
+	if (!l2->rx_callback || !packet || hdr.caplen < sizeof(*ethhdr))
 		return;
 
 	ethhdr = (struct l2_ethhdr *) packet;
@@ -152,7 +152,7 @@ static void l2_packet_receive_cb(u_char *user, const struct pcap_pkthdr *hdr,
 	unsigned char *buf;
 	size_t len;
 
-	if (pkt_data == NULL || hdr->caplen < sizeof(*ethhdr))
+	if (!l2->rx_callback || !pkt_data || hdr->caplen < sizeof(*ethhdr))
 		return;
 
 	ethhdr = (struct l2_ethhdr *) pkt_data;

src/l2_packet/l2_packet_privsep.c

@@ -216,7 +216,8 @@ struct l2_packet_data * l2_packet_init(
 	}
 	os_memcpy(l2->own_addr, reply, ETH_ALEN);
 
-	eloop_register_read_sock(l2->fd, l2_packet_receive, l2, NULL);
+	if (rx_callback)
+		eloop_register_read_sock(l2->fd, l2_packet_receive, l2, NULL);
 
 	return l2;
 

src/l2_packet/l2_packet_winpcap.c

@@ -224,6 +224,9 @@ struct l2_packet_data * l2_packet_init(
 		return NULL;
 	}
 
+	if (!rx_callback)
+		return l2;
+
 	l2->rx_avail = CreateEvent(NULL, TRUE, FALSE, NULL);
 	l2->rx_done = CreateEvent(NULL, TRUE, FALSE, NULL);
 	l2->rx_notify = CreateEvent(NULL, TRUE, FALSE, NULL);