NET: pass source IP address to packet handlers

This is needed for the upcoming TFTP server implementation.

This also simplifies PingHandler() and fixes rxhand_f documentation.

Signed-off-by: Luca Ceresoli <luca.ceresoli@comelit.it>
Cc: Wolfgang Denk <wd@denx.de>
Acked-by: Detlev Zundel <dzu@denx.de>

net/dns.c

@@ -101,7 +101,7 @@ DnsTimeout(void)
 }
 
 static void
-DnsHandler(uchar *pkt, unsigned dest, unsigned src, unsigned len)
+DnsHandler(uchar *pkt, unsigned dest, IPaddr_t sip, unsigned src, unsigned len)
 {
 	struct header *header;
 	const unsigned char *p, *e, *s;