ping: fix IPv6 pinging. Closes bug 3187

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/networking/ping.c b/networking/ping.c
index 11ce24e..28ccbb0 100644
--- a/networking/ping.c
+++ b/networking/ping.c
@@ -484,7 +484,7 @@
 #if ENABLE_PING6
 static void sendping6(int junk UNUSED_PARAM)
 {
-	struct icmp6_hdr *pkt = alloca(datalen + sizeof(struct icmp6_hdr) + 4);
+	struct icmp6_hdr *pkt = G.snd_packet;
 
 	//memset(pkt, 0, datalen + sizeof(struct icmp6_hdr) + 4);
 	pkt->icmp6_type = ICMP6_ECHO_REQUEST;