1 files changed, 83 insertions, 0 deletions
diff --git a/src/cmd/ip/snoopy/gre.c b/src/cmd/ip/snoopy/gre.c
new file mode 100755
index 00000000..908d1553
--- /dev/null
+++ b/src/cmd/ip/snoopy/gre.c
@@ -0,0 +1,83 @@
+
+/* GRE flag bits */
+enum {
+	GRE_chksum	= (1<<15),
+	GRE_routing	= (1<<14),
+	GRE_key		= (1<<13),
+	GRE_seq		= (1<<12),
+	GRE_srcrt	= (1<<11),
+	GRE_recur	= (7<<8),
+	GRE_ack		= (1<<7),
+	GRE_ver		= 0x7,
+};
+
+/* GRE protocols */
+enum {
+	GRE_sna		= 0x0004,
+	GRE_osi		= 0x00fe,
+	GRE_pup		= 0x0200,
+	GRE_xns		= 0x0600,
+	GRE_ip		= 0x0800,
+	GRE_chaos	= 0x0804,
+	GRE_rfc826	= 0x0806,
+	GRE_frarp	= 0x0808,
+	GRE_vines	= 0x0bad,
+	GRE_vinesecho	= 0x0bae,
+	GRE_vinesloop	= 0x0baf,
+	GRE_decnetIV	= 0x6003,
+	GRE_ppp		= 0x880b,
+};
+
+int
+sprintgre(void *a, char *buf, int len)
+{
+	int flag, prot, chksum, offset, key, seq, ack;
+	int n;
+	uchar *p = a;
+
+	chksum = offset = key = seq = ack = 0;
+	
+	flag = NetS(p);
+	prot = NetS(p+2);
+	p += 4; len -= 4;
+	if(flag & (GRE_chksum|GRE_routing)){
+		chksum = NetS(p);
+		offset = NetS(p+2);
+		p += 4; len -= 4;
+	}
+	if(flag&GRE_key){
+		key = NetL(p);
+		p += 4; len -= 4;
+	}
+	if(flag&GRE_seq){
+		seq = NetL(p);
+		p += 4; len -= 4;
+	}
+	if(flag&GRE_ack){
+		ack = NetL(p);
+		p += 4; len -= 4;
+	}
+	/* skip routing if present */
+	if(flag&GRE_routing) {
+		while(len >= 4 && (n=p[3]) != 0) {
+			len -= n;
+			p += n;
+		}
+	}
+
+	USED(offset);
+	USED(chksum);
+
+	n = sprint(buf, "GRE(f %4.4ux p %ux k %ux", flag, prot, key);
+	if(flag&GRE_seq)
+		n += sprint(buf+n, " s %ux", seq);
+	if(flag&GRE_ack)
+		n += sprint(buf+n, " a %ux", ack);
+	n += sprint(buf+n, " len = %d/%d) ", len, key>>16);
+	if(prot == GRE_ppp && len > 0)
+		n += sprintppp(p, buf+n, len);
+	else
+		n += sprintx(p, buf+n, len);
+		
+	return n;
+}