The Tcpdump Group git mirrors - tcpdump/blob - print-zeromq.c

   1 /*
   2  * This file implements decoding of ZeroMQ network protocol(s).
   3  *
   4  *
   5  * Copyright (c) 2013 The TCPDUMP project
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  18  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  19  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  20  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  21  * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  23  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  24  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  25  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  27  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  28  * POSSIBILITY OF SUCH DAMAGE.
  29  */
  30
  31 #ifdef HAVE_CONFIG_H
  32 #include "config.h"
  33 #endif
  34
  35 #include <netdissect-stdinc.h>
  36
  37 #include "netdissect.h"
  38 #include "extract.h"
  39
  40 static const char tstr[] = " [|zmtp1]";
  41
  42 /* Maximum number of ZMTP/1.0 frame body bytes (without the flags) to dump in
  43  * hex and ASCII under a single "-v" flag.
  44  */
  45 #define VBYTES 128
  46
  47 /*
  48  * Below is an excerpt from the "13/ZMTP" specification:
  49  *
  50  * A ZMTP message consists of 1 or more frames.
  51  *
  52  * A ZMTP frame consists of a length, followed by a flags field and a frame
  53  * body of (length - 1) octets. Note: the length includes the flags field, so
  54  * an empty frame has a length of 1.
  55  *
  56  * For frames with a length of 1 to 254 octets, the length SHOULD BE encoded
  57  * as a single octet. The minimum valid length of a frame is 1 octet, thus a
  58  * length of 0 is invalid and such frames SHOULD be discarded silently.
  59  *
  60  * For frames with lengths of 255 and greater, the length SHALL BE encoded as
  61  * a single octet with the value 255, followed by the length encoded as a
  62  * 64-bit unsigned integer in network byte order. For frames with lengths of
  63  * 1 to 254 octets this encoding MAY be also used.
  64  *
  65  * The flags field consists of a single octet containing various control
  66  * flags. Bit 0 is the least significant bit.
  67  *
  68  * - Bit 0 (MORE): More frames to follow. A value of 0 indicates that there
  69  *   are no more frames to follow. A value of 1 indicates that more frames
  70  *   will follow. On messages consisting of a single frame the MORE flag MUST
  71  *   be 0.
  72  *
  73  * - Bits 1-7: Reserved. Bits 1-7 are reserved for future use and SHOULD be
  74  *   zero.
  75  */
  76
  77 static const u_char *
  78 zmtp1_print_frame(netdissect_options *ndo, const u_char *cp, const u_char *ep)
  79 {
  80         uint64_t body_len_declared, body_len_captured, header_len;
  81         uint8_t flags;
  82
  83         ND_PRINT((ndo, "\n\t"));
  84         ND_TCHECK2(*cp, 1); /* length/0xFF */
  85
  86         if (cp[0] != 0xFF) {
  87                 header_len = 1; /* length */
  88                 body_len_declared = cp[0];
  89                 ND_PRINT((ndo, " frame flags+body  (8-bit) length %" PRIu64, body_len_declared));
  90         } else {
  91                 header_len = 1 + 8; /* 0xFF, length */
  92                 ND_PRINT((ndo, " frame flags+body (64-bit) length"));
  93                 ND_TCHECK2(*cp, header_len); /* 0xFF, length */
  94                 body_len_declared = EXTRACT_64BITS(cp + 1);
  95                 ND_PRINT((ndo, " %" PRIu64, body_len_declared));
  96         }
  97         if (body_len_declared == 0)
  98                 return cp + header_len; /* skip to the next frame */
  99         ND_TCHECK2(*cp, header_len + 1); /* ..., flags */
 100         flags = cp[header_len];
 101
 102         body_len_captured = ep - cp - header_len;
 103         if (body_len_declared > body_len_captured)
 104                 ND_PRINT((ndo, " (%" PRIu64 " captured)", body_len_captured));
 105         ND_PRINT((ndo, ", flags 0x%02x", flags));
 106
 107         if (ndo->ndo_vflag) {
 108                 uint64_t body_len_printed = min(body_len_captured, body_len_declared);
 109
 110                 ND_PRINT((ndo, " (%s|%s|%s|%s|%s|%s|%s|%s)",
 111                         flags & 0x80 ? "MBZ" : "-",
 112                         flags & 0x40 ? "MBZ" : "-",
 113                         flags & 0x20 ? "MBZ" : "-",
 114                         flags & 0x10 ? "MBZ" : "-",
 115                         flags & 0x08 ? "MBZ" : "-",
 116                         flags & 0x04 ? "MBZ" : "-",
 117                         flags & 0x02 ? "MBZ" : "-",
 118                         flags & 0x01 ? "MORE" : "-"));
 119
 120                 if (ndo->ndo_vflag == 1)
 121                         body_len_printed = min(VBYTES + 1, body_len_printed);
 122                 if (body_len_printed > 1) {
 123                         ND_PRINT((ndo, ", first %" PRIu64 " byte(s) of body:", body_len_printed - 1));
 124                         hex_and_ascii_print(ndo, "\n\t ", cp + header_len + 1, body_len_printed - 1);
 125                         ND_PRINT((ndo, "\n"));
 126                 }
 127         }
 128
 129         ND_TCHECK2(*cp, header_len + body_len_declared); /* Next frame within the buffer ? */
 130         return cp + header_len + body_len_declared;
 131
 132 trunc:
 133         ND_PRINT((ndo, "%s", tstr));
 134         return ep;
 135 }
 136
 137 void
 138 zmtp1_print(netdissect_options *ndo, const u_char *cp, u_int len)
 139 {
 140         const u_char *ep = min(ndo->ndo_snapend, cp + len);
 141
 142         ND_PRINT((ndo, ": ZMTP/1.0"));
 143         while (cp < ep)
 144                 cp = zmtp1_print_frame(ndo, cp, ep);
 145 }
 146
 147 /* The functions below decode a ZeroMQ datagram, supposedly stored in the "Data"
 148  * field of an ODATA/RDATA [E]PGM packet. An excerpt from zmq_pgm(7) man page
 149  * follows.
 150  *
 151  * In order for late joining consumers to be able to identify message
 152  * boundaries, each PGM datagram payload starts with a 16-bit unsigned integer
 153  * in network byte order specifying either the offset of the first message frame
 154  * in the datagram or containing the value 0xFFFF if the datagram contains
 155  * solely an intermediate part of a larger message.
 156  *
 157  * Note that offset specifies where the first message begins rather than the
 158  * first message part. Thus, if there are trailing message parts at the
 159  * beginning of the packet the offset ignores them and points to first initial
 160  * message part in the packet.
 161  */
 162
 163 static const u_char *
 164 zmtp1_print_intermediate_part(netdissect_options *ndo, const u_char *cp, const u_int len)
 165 {
 166         u_int frame_offset;
 167         uint64_t remaining_len;
 168
 169         ND_TCHECK2(*cp, 2);
 170         frame_offset = EXTRACT_16BITS(cp);
 171         ND_PRINT((ndo, "\n\t frame offset 0x%04x", frame_offset));
 172         cp += 2;
 173         remaining_len = ndo->ndo_snapend - cp; /* without the frame length */
 174
 175         if (frame_offset == 0xFFFF)
 176                 frame_offset = len - 2; /* always within the declared length */
 177         else if (2 + frame_offset > len) {
 178                 ND_PRINT((ndo, " (exceeds datagram declared length)"));
 179                 goto trunc;
 180         }
 181
 182         /* offset within declared length of the datagram */
 183         if (frame_offset) {
 184                 ND_PRINT((ndo, "\n\t frame intermediate part, %u bytes", frame_offset));
 185                 if (frame_offset > remaining_len)
 186                         ND_PRINT((ndo, " (%"PRIu64" captured)", remaining_len));
 187                 if (ndo->ndo_vflag) {
 188                         uint64_t len_printed = min(frame_offset, remaining_len);
 189
 190                         if (ndo->ndo_vflag == 1)
 191                                 len_printed = min(VBYTES, len_printed);
 192                         if (len_printed > 1) {
 193                                 ND_PRINT((ndo, ", first %"PRIu64" byte(s):", len_printed));
 194                                 hex_and_ascii_print(ndo, "\n\t ", cp, len_printed);
 195                                 ND_PRINT((ndo, "\n"));
 196                         }
 197                 }
 198         }
 199         return cp + frame_offset;
 200
 201 trunc:
 202         ND_PRINT((ndo, "%s", tstr));
 203         return cp + len;
 204 }
 205
 206 void
 207 zmtp1_print_datagram(netdissect_options *ndo, const u_char *cp, const u_int len)
 208 {
 209         const u_char *ep = min(ndo->ndo_snapend, cp + len);
 210
 211         cp = zmtp1_print_intermediate_part(ndo, cp, len);
 212         while (cp < ep)
 213                 cp = zmtp1_print_frame(ndo, cp, ep);
 214 }