nexmon – Rev 1
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/*
* This file implements decoding of ZeroMQ network protocol(s).
*
*
* 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.
*/
#define NETDISSECT_REWORKED
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <tcpdump-stdinc.h>
#include "interface.h"
#include "extract.h"
static const char tstr[] = " [|zmtp1]";
/* 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((ndo, "\n\t"));
ND_TCHECK2(*cp, 1); /* length/0xFF */
if (cp[0] != 0xFF) {
header_len = 1; /* length */
body_len_declared = cp[0];
if (body_len_declared == 0)
return cp + header_len; /* skip to next frame */
ND_PRINT((ndo, " frame flags+body (8-bit) length %u", cp[0]));
ND_TCHECK2(*cp, header_len + 1); /* length, flags */
flags = cp[1];
} else {
header_len = 1 + 8; /* 0xFF, length */
ND_PRINT((ndo, " frame flags+body (64-bit) length"));
ND_TCHECK2(*cp, header_len); /* 0xFF, length */
body_len_declared = EXTRACT_64BITS(cp + 1);
if (body_len_declared == 0)
return cp + header_len; /* skip to next frame */
ND_PRINT((ndo, " %" PRIu64, body_len_declared));
ND_TCHECK2(*cp, header_len + 1); /* 0xFF, length, flags */
flags = cp[9];
}
body_len_captured = ep - cp - header_len;
if (body_len_declared > body_len_captured)
ND_PRINT((ndo, " (%" PRIu64 " captured)", body_len_captured));
ND_PRINT((ndo, ", flags 0x%02x", flags));
if (ndo->ndo_vflag) {
uint64_t body_len_printed = min(body_len_captured, body_len_declared);
ND_PRINT((ndo, " (%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 = min(VBYTES + 1, body_len_printed);
if (body_len_printed > 1) {
ND_PRINT((ndo, ", 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);
ND_PRINT((ndo, "\n"));
}
}
ND_TCHECK2(*cp, header_len + body_len_declared); /* Next frame within the buffer ? */
return cp + header_len + body_len_declared;
trunc:
ND_PRINT((ndo, "%s", tstr));
return ep;
}
void
zmtp1_print(netdissect_options *ndo, const u_char *cp, u_int len)
{
const u_char *ep = min(ndo->ndo_snapend, cp + len);
ND_PRINT((ndo, ": 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;
uint64_t remaining_len;
ND_TCHECK2(*cp, 2);
frame_offset = EXTRACT_16BITS(cp);
ND_PRINT((ndo, "\n\t frame offset 0x%04x", frame_offset));
cp += 2;
remaining_len = ndo->ndo_snapend - 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((ndo, " (exceeds datagram declared length)"));
goto trunc;
}
/* offset within declared length of the datagram */
if (frame_offset) {
ND_PRINT((ndo, "\n\t frame intermediate part, %u bytes", frame_offset));
if (frame_offset > remaining_len)
ND_PRINT((ndo, " (%"PRIu64" captured)", remaining_len));
if (ndo->ndo_vflag) {
uint64_t len_printed = min(frame_offset, remaining_len);
if (ndo->ndo_vflag == 1)
len_printed = min(VBYTES, len_printed);
if (len_printed > 1) {
ND_PRINT((ndo, ", first %"PRIu64" byte(s):", len_printed));
hex_and_ascii_print(ndo, "\n\t ", cp, len_printed);
ND_PRINT((ndo, "\n"));
}
}
}
return cp + frame_offset;
trunc:
ND_PRINT((ndo, "%s", tstr));
return cp + len;
}
void
zmtp1_print_datagram(netdissect_options *ndo, const u_char *cp, const u_int len)
{
const u_char *ep = min(ndo->ndo_snapend, cp + len);
cp = zmtp1_print_intermediate_part(ndo, cp, len);
while (cp < ep)
cp = zmtp1_print_frame(ndo, cp, ep);
}