net: introduce packet capture support

Add support for capturing ethernet packets and storing
them in memory in PCAP(2.4) format, later to be analyzed by
any PCAP viewer software (IE. Wireshark)

This feature greatly assist debugging network issues such
as detecting dropped packets, packet corruption etc.

Signed-off-by: Ramon Fried <rfried.dev@gmail.com>
Reviewed-by: Alex Marginean <alexm.osslist@gmail.com>
Tested-by: Alex Marginean <alexm.osslist@gmail.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>

net/net.c

@@ -96,6 +96,9 @@
 #include <net.h>
 #include <net/fastboot.h>
 #include <net/tftp.h>
+#if defined(CONFIG_CMD_PCAP)
+#include <net/pcap.h>
+#endif
 #if defined(CONFIG_LED_STATUS)
 #include <miiphy.h>
 #include <status_led.h>
@@ -672,6 +675,11 @@ done:
 	net_set_icmp_handler(NULL);
 #endif
 	net_set_state(prev_net_state);
+
+#if defined(CONFIG_CMD_PCAP)
+	if (pcap_active())
+		pcap_print_status();
+#endif
 	return ret;
 }
 
@@ -1084,6 +1092,9 @@ void net_process_received_packet(uchar *in_packet, int len)
 
 	debug_cond(DEBUG_NET_PKT, "packet received\n");
 
+#if defined(CONFIG_CMD_PCAP)
+	pcap_post(in_packet, len, false);
+#endif
 	net_rx_packet = in_packet;
 	net_rx_packet_len = len;
 	et = (struct ethernet_hdr *)in_packet;