summaryrefslogtreecommitdiff
path: root/print-zeromq.c
blob: 2cf9d6c3ffabdfaaec75be0a960bf1af4c3624f9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
/*
 * Copyright (c) 2013 The TCPDUMP project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/* \summary: ZeroMQ Message Transport Protocol (ZMTP) printer */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include "netdissect-stdinc.h"

#include "netdissect.h"
#include "extract.h"


/* Maximum number of ZMTP/1.0 frame body bytes (without the flags) to dump in
 * hex and ASCII under a single "-v" flag.
 */
#define VBYTES 128

/*
 * Below is an excerpt from the "13/ZMTP" specification:
 *
 * A ZMTP message consists of 1 or more frames.
 *
 * A ZMTP frame consists of a length, followed by a flags field and a frame
 * body of (length - 1) octets. Note: the length includes the flags field, so
 * an empty frame has a length of 1.
 *
 * For frames with a length of 1 to 254 octets, the length SHOULD BE encoded
 * as a single octet. The minimum valid length of a frame is 1 octet, thus a
 * length of 0 is invalid and such frames SHOULD be discarded silently.
 *
 * For frames with lengths of 255 and greater, the length SHALL BE encoded as
 * a single octet with the value 255, followed by the length encoded as a
 * 64-bit unsigned integer in network byte order. For frames with lengths of
 * 1 to 254 octets this encoding MAY be also used.
 *
 * The flags field consists of a single octet containing various control
 * flags. Bit 0 is the least significant bit.
 *
 * - Bit 0 (MORE): More frames to follow. A value of 0 indicates that there
 *   are no more frames to follow. A value of 1 indicates that more frames
 *   will follow. On messages consisting of a single frame the MORE flag MUST
 *   be 0.
 *
 * - Bits 1-7: Reserved. Bits 1-7 are reserved for future use and SHOULD be
 *   zero.
 */

static const u_char *
zmtp1_print_frame(netdissect_options *ndo, const u_char *cp, const u_char *ep)
{
	uint64_t body_len_declared, body_len_captured, header_len;
	uint8_t flags;

	ND_PRINT("\n\t");

	if (GET_U_1(cp) != 0xFF) {	/* length/0xFF */
		header_len = 1; /* length */
		body_len_declared = GET_U_1(cp);
		ND_PRINT(" frame flags+body  (8-bit) length %" PRIu64, body_len_declared);
	} else {
		header_len = 1 + 8; /* 0xFF, length */
		ND_PRINT(" frame flags+body (64-bit) length");
		ND_TCHECK_LEN(cp, header_len); /* 0xFF, length */
		body_len_declared = GET_BE_U_8(cp + 1);
		ND_PRINT(" %" PRIu64, body_len_declared);
	}
	if (body_len_declared == 0)
		return cp + header_len; /* skip to the next frame */
	ND_TCHECK_LEN(cp, header_len + 1); /* ..., flags */
	flags = GET_U_1(cp + header_len);

	body_len_captured = ep - cp - header_len;
	if (body_len_declared > body_len_captured)
		ND_PRINT(" (%" PRIu64 " captured)", body_len_captured);
	ND_PRINT(", flags 0x%02x", flags);

	if (ndo->ndo_vflag) {
		uint64_t body_len_printed = ND_MIN(body_len_captured, body_len_declared);

		ND_PRINT(" (%s|%s|%s|%s|%s|%s|%s|%s)",
			flags & 0x80 ? "MBZ" : "-",
			flags & 0x40 ? "MBZ" : "-",
			flags & 0x20 ? "MBZ" : "-",
			flags & 0x10 ? "MBZ" : "-",
			flags & 0x08 ? "MBZ" : "-",
			flags & 0x04 ? "MBZ" : "-",
			flags & 0x02 ? "MBZ" : "-",
			flags & 0x01 ? "MORE" : "-");

		if (ndo->ndo_vflag == 1)
			body_len_printed = ND_MIN(VBYTES + 1, body_len_printed);
		if (body_len_printed > 1) {
			ND_PRINT(", first %" PRIu64 " byte(s) of body:", body_len_printed - 1);
			hex_and_ascii_print(ndo, "\n\t ", cp + header_len + 1, body_len_printed - 1);
		}
	}

	/*
	 * Do not advance cp by the sum of header_len and body_len_declared
	 * before each offset has successfully passed ND_TCHECK_LEN() as the
	 * sum can roll over (9 + 0xfffffffffffffff7 = 0) and cause an
	 * infinite loop.
	 */
	cp += header_len;
	ND_TCHECK_LEN(cp, body_len_declared); /* Next frame within the buffer ? */
	return cp + body_len_declared;

trunc:
	nd_print_trunc(ndo);
	return ep;
}

void
zmtp1_print(netdissect_options *ndo, const u_char *cp, u_int len)
{
	const u_char *ep = ND_MIN(ndo->ndo_snapend, cp + len);

	ndo->ndo_protocol = "zmtp1";
	ND_PRINT(": ZMTP/1.0");
	while (cp < ep)
		cp = zmtp1_print_frame(ndo, cp, ep);
}

/* 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_print_trunc(ndo);
	return cp + len;
}

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);
}