Revert "Ethernet: Remove two useless tests"

This reverts commit b7fff70 (partially)

The sanity check in print.c/pretty_print_packet() function, packet length
(length) >= capture length (caplen), apply when the ether_print()
function is called by ether_if_print(), netanalyzer_if_print() or
netanalyzer_transparent_if_print().

But the ether_print() function is called in some other cases, thus not
sure length always >= caplen.

Author: fxlb

print-ether.c

@@ -163,6 +163,10 @@ ether_print(netdissect_options *ndo,
 		nd_print_trunc(ndo);
 		return (caplen);
 	}
+	if (length < ETHER_HDRLEN) {
+		nd_print_trunc(ndo);
+		return (length);
+	}
 
 	if (ndo->ndo_eflag) {
 		if (print_encap_header != NULL)
@@ -210,6 +214,11 @@ ether_print(netdissect_options *ndo,
 			nd_print_trunc(ndo);
 			return (hdrlen + caplen);
 		}
+		if (length < 4) {
+			ndo->ndo_protocol = "vlan";
+			nd_print_trunc(ndo);
+			return (hdrlen + length);
+		}
 	        if (ndo->ndo_eflag) {
 			uint16_t tag = EXTRACT_BE_U_2(p);