refine 802.1Q VLAN TCI decoding

Factor the common code out to a new function and rename the CFI bit to
DEI to match the terminology in Clause 9.6 of IEEE 802.1Q-2011.

1 files changed, 12 insertions, 0 deletions

diff --git a/addrtoname.c b/addrtoname.c
index f6e070e7..d0437fe4 100644
--- a/addrtoname.c
+++ b/addrtoname.c
@@ -1215,3 +1215,15 @@ newh6namemem(void)
 	return (p);
 }
 #endif /* INET6 */
+
+/* Represent TCI part of the 802.1Q 4-octet tag as text. */
+const char *
+ieee8021q_tci_string(const uint16_t tci)
+{
+	static char buf[128];
+	snprintf(buf, sizeof(buf), "vlan %u, p %u%s",
+	         tci & 0xfff,
+	         tci >> 13,
+	         (tci & 0x1000) ? ", DEI" : "");
+	return buf;
+}