+/* The functions below decode a ZeroMQ datagram, supposedly stored in the "Data"
+ * field of an ODATA/RDATA [E]PGM packet. An excerpt from zmq_pgm(7) man page
+ * follows.
+ *
+ * In order for late joining consumers to be able to identify message
+ * boundaries, each PGM datagram payload starts with a 16-bit unsigned integer
+ * in network byte order specifying either the offset of the first message frame
+ * in the datagram or containing the value 0xFFFF if the datagram contains
+ * solely an intermediate part of a larger message.
+ *
+ * Note that offset specifies where the first message begins rather than the
+ * first message part. Thus, if there are trailing message parts at the
+ * beginning of the packet the offset ignores them and points to first initial
+ * message part in the packet.
+ */
+
+static const u_char *
+zmtp1_print_intermediate_part(netdissect_options *ndo, const u_char *cp, const u_int len)
+{
+ u_int frame_offset;
+ u_int remaining_len;
+
+ frame_offset = GET_BE_U_2(cp);
+ ND_PRINT("\n\t frame offset 0x%04x", frame_offset);
+ cp += 2;
+ remaining_len = ND_BYTES_AVAILABLE_AFTER(cp); /* without the frame length */
+
+ if (frame_offset == 0xFFFF)
+ frame_offset = len - 2; /* always within the declared length */
+ else if (2 + frame_offset > len) {
+ ND_PRINT(" (exceeds datagram declared length)");
+ goto trunc;
+ }
+
+ /* offset within declared length of the datagram */
+ if (frame_offset) {
+ ND_PRINT("\n\t frame intermediate part, %u bytes", frame_offset);
+ if (frame_offset > remaining_len)
+ ND_PRINT(" (%u captured)", remaining_len);
+ if (ndo->ndo_vflag) {
+ u_int len_printed = ND_MIN(frame_offset, remaining_len);
+
+ if (ndo->ndo_vflag == 1)
+ len_printed = ND_MIN(VBYTES, len_printed);
+ if (len_printed > 1) {
+ ND_PRINT(", first %u byte(s):", len_printed);
+ hex_and_ascii_print(ndo, "\n\t ", cp, len_printed);
+ }
+ }
+ }
+ return cp + frame_offset;
+
+trunc:
+ nd_trunc_longjmp(ndo);
+}
+
+void
+zmtp1_datagram_print(netdissect_options *ndo, const u_char *cp, const u_int len)
+{
+ const u_char *ep = ND_MIN(ndo->ndo_snapend, cp + len);
+
+ ndo->ndo_protocol = "zmtp1";
+ cp = zmtp1_print_intermediate_part(ndo, cp, len);
+ while (cp < ep)
+ cp = zmtp1_print_frame(ndo, cp, ep);
+}