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 <tcpdump-stdinc.h>
  36
  37 #include <stdio.h>
  38
  39 #include "interface.h"
  40 #include "extract.h"
  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(const u_char *cp, const u_char *ep) {
  79         u_int64_t body_len_declared, body_len_captured, header_len;
  80         u_int8_t flags;
  81
  82         printf("\n\t");
  83         TCHECK2(*cp, 1); /* length/0xFF */
  84
  85         if (cp[0] != 0xFF) {
  86                 header_len = 1; /* length */
  87                 body_len_declared = cp[0];
  88                 if (body_len_declared == 0)
  89                         return cp + header_len; /* skip to next frame */
  90                 printf(" frame flags+body  (8-bit) length %u", cp[0]);
  91                 TCHECK2(*cp, header_len + 1); /* length, flags */
  92                 flags = cp[1];
  93         } else {
  94                 header_len = 1 + 8; /* 0xFF, length */
  95                 printf(" frame flags+body (64-bit) length");
  96                 TCHECK2(*cp, header_len); /* 0xFF, length */
  97                 body_len_declared = EXTRACT_64BITS(cp + 1);
  98                 if (body_len_declared == 0)
  99                         return cp + header_len; /* skip to next frame */
 100                 printf(" %" PRIu64, body_len_declared);
 101                 TCHECK2(*cp, header_len + 1); /* 0xFF, length, flags */
 102                 flags = cp[9];
 103         }
 104
 105         body_len_captured = ep - cp - header_len;
 106         if (body_len_declared > body_len_captured)
 107                 printf(" (%" PRIu64 " captured)", body_len_captured);
 108         printf(", flags 0x%02x", flags);
 109
 110         if (vflag) {
 111                 u_int64_t body_len_printed = MIN(body_len_captured, body_len_declared);
 112
 113                 printf(" (%s|%s|%s|%s|%s|%s|%s|%s)",
 114                         flags & 0x80 ? "MBZ" : "-",
 115                         flags & 0x40 ? "MBZ" : "-",
 116                         flags & 0x20 ? "MBZ" : "-",
 117                         flags & 0x10 ? "MBZ" : "-",
 118                         flags & 0x08 ? "MBZ" : "-",
 119                         flags & 0x04 ? "MBZ" : "-",
 120                         flags & 0x02 ? "MBZ" : "-",
 121                         flags & 0x01 ? "MORE" : "-");
 122
 123                 if (vflag == 1)
 124                         body_len_printed = MIN(VBYTES + 1, body_len_printed);
 125                 if (body_len_printed > 1) {
 126                         printf(", first %" PRIu64 " byte(s) of body:", body_len_printed - 1);
 127                         hex_and_ascii_print("\n\t ", cp + header_len + 1, body_len_printed - 1);
 128                         printf("\n");
 129                 }
 130         }
 131
 132         TCHECK2(*cp, header_len + body_len_declared); /* Next frame within the buffer ? */
 133         return cp + header_len + body_len_declared;
 134
 135 trunc:
 136         printf(" [|zmtp1]");
 137         return ep;
 138 }
 139
 140 void
 141 zmtp1_print(const u_char *cp, u_int len) {
 142         const u_char *ep = MIN(snapend, cp + len);
 143
 144         printf(": ZMTP/1.0");
 145         while (cp < ep)
 146                 cp = zmtp1_print_frame(cp, ep);
 147 }
 148
 149 /* The functions below decode a ZeroMQ datagram, supposedly stored in the "Data"
 150  * field of an ODATA/RDATA [E]PGM packet. An excerpt from zmq_pgm(7) man page
 151  * follows.
 152  *
 153  * In order for late joining consumers to be able to identify message
 154  * boundaries, each PGM datagram payload starts with a 16-bit unsigned integer
 155  * in network byte order specifying either the offset of the first message frame
 156  * in the datagram or containing the value 0xFFFF if the datagram contains
 157  * solely an intermediate part of a larger message.
 158  *
 159  * Note that offset specifies where the first message begins rather than the
 160  * first message part. Thus, if there are trailing message parts at the
 161  * beginning of the packet the offset ignores them and points to first initial
 162  * message part in the packet.
 163  */
 164
 165 static const u_char *
 166 zmtp1_print_intermediate_part(const u_char *cp, const u_int len) {
 167         u_int frame_offset;
 168         u_int64_t remaining_len;
 169
 170         TCHECK2(*cp, 2);
 171         frame_offset = EXTRACT_16BITS(cp);
 172         printf("\n\t frame offset 0x%04x", frame_offset);
 173         cp += 2;
 174         remaining_len = snapend - cp; /* without the frame length */
 175
 176         if (frame_offset == 0xFFFF)
 177                 frame_offset = len - 2; /* always within the declared length */
 178         else if (2 + frame_offset > len) {
 179                 printf(" (exceeds datagram declared length)");
 180                 goto trunc;
 181         }
 182
 183         /* offset within declared length of the datagram */
 184         if (frame_offset) {
 185                 printf("\n\t frame intermediate part, %u bytes", frame_offset);
 186                 if (frame_offset > remaining_len)
 187                         printf(" (%"PRIu64" captured)", remaining_len);
 188                 if (vflag) {
 189                         u_int64_t len_printed = MIN(frame_offset, remaining_len);
 190
 191                         if (vflag == 1)
 192                                 len_printed = MIN(VBYTES, len_printed);
 193                         if (len_printed > 1) {
 194                                 printf(", first %"PRIu64" byte(s):", len_printed);
 195                                 hex_and_ascii_print("\n\t ", cp, len_printed);
 196                                 printf("\n");
 197                         }
 198                 }
 199         }
 200         return cp + frame_offset;
 201
 202 trunc:
 203         printf(" [|zmtp1]");
 204         return cp + len;
 205 }
 206
 207 void
 208 zmtp1_print_datagram(const u_char *cp, const u_int len) {
 209         const u_char *ep = MIN(snapend, cp + len);
 210
 211         cp = zmtp1_print_intermediate_part(cp, len);
 212         while (cp < ep)
 213                 cp = zmtp1_print_frame(cp, ep);
 214 }