slow: Add OSSP support

Add basic printing of "Organization Specific Slow Protocol" (OSSP),
which is standardized in IEEE 802.3 Annex 57B. Since this is used for
non-standardized protocols and thus carries mostly unknown-structured
data, most of the packet is still printed verbatim.

Author: corubba

print-slow.c

@@ -34,6 +34,7 @@
 #define	SLOW_PROTO_LACP                     1
 #define	SLOW_PROTO_MARKER                   2
 #define SLOW_PROTO_OAM                      3
+#define SLOW_PROTO_OSSP                    10
 
 #define	LACP_VERSION                        1
 #define	MARKER_VERSION                      1
@@ -42,6 +43,7 @@ static const struct tok slow_proto_values[] = {
     { SLOW_PROTO_LACP, "LACP" },
     { SLOW_PROTO_MARKER, "MARKER" },
     { SLOW_PROTO_OAM, "OAM" },
+    { SLOW_PROTO_OSSP, "OSSP" },
     { 0, NULL}
 };
 
@@ -239,6 +241,7 @@ struct lacp_marker_tlv_terminator_t {
 
 static void slow_marker_lacp_print(netdissect_options *, const u_char *, u_int, u_int);
 static void slow_oam_print(netdissect_options *, const u_char *, u_int);
+static void slow_ossp_print(netdissect_options *, const u_char *, u_int);
 
 void
 slow_print(netdissect_options *ndo,
@@ -278,7 +281,8 @@ slow_print(netdissect_options *ndo,
         print_version = 1;
         break;
 
-    case SLOW_PROTO_OAM: /* fall through */
+    case SLOW_PROTO_OAM:
+    case SLOW_PROTO_OSSP:
         print_version = 0;
         break;
 
@@ -313,6 +317,13 @@ slow_print(netdissect_options *ndo,
     default: /* should not happen */
         break;
 
+    case SLOW_PROTO_OSSP:
+        /* skip subtype */
+        len -= 1;
+        pptr += 1;
+        slow_ossp_print(ndo, pptr, len);
+        break;
+
     case SLOW_PROTO_OAM:
         /* skip subtype */
         len -= 1;
@@ -733,3 +744,29 @@ slow_oam_print(netdissect_options *ndo,
 tooshort:
     ND_PRINT("\n\t\t packet is too short");
 }
+
+/*
+ * Print Organization Specific Slow Protocol. (802.3 Annex 57B)
+ */
+static void
+slow_ossp_print(netdissect_options *ndo,
+                const u_char *tptr, u_int tlen)
+{
+    uint32_t oui;
+
+    ND_ICHECKMSG_U("length", tlen, <, 3);
+
+    oui = GET_BE_U_3(tptr);
+    ND_PRINT("\n\tOUI: %s (0x%06x)",
+             tok2str(oui_values, "Unknown", oui),
+             oui);
+    tlen -= 3;
+    tptr += 3;
+
+    print_unknown_data(ndo, tptr, "\n\t", tlen);
+
+    return;
+
+invalid:
+    nd_print_invalid(ndo);
+}

tests/TESTLIST

@@ -505,6 +505,7 @@ lldp_mud-v	lldp_mudurl.pcap	lldp_mudurl-v.out	-e -v
 lldp_mud-vv	lldp_mudurl.pcap	lldp_mudurl-vv.out	-e -vv
 lldp_8021_linkagg-v  lldp_8021_linkagg.pcap lldp_8021_linkagg-v.out  -v
 lldp_8021_linkagg-vv lldp_8021_linkagg.pcap lldp_8021_linkagg-vv.out -vv
+slow-ossp	slow-ossp.pcap	slow-ossp.out	-v
 # fuzzed pcap
 udld-inf-loop-1-v  udld-inf-loop-1.pcapng  udld-inf-loop-1-v.out  -v
 

tests/slow-ossp.out

@@ -0,0 +1,5 @@
+    1  2025-09-23 15:00:00.000000 OSSP, length 52
+	OUI: Unknown (0x0019a7)
+	0x0000:  0001 1000 0000 0100 0404 0000 0000 0000
+	0x0010:  0000 0000 0000 0000 0000 0000 0000 0000
+	0x0020:  0000 0000 0000 0000 0000 0000 0000 0000