876 lines
32 KiB
C
876 lines
32 KiB
C
/* packet-vj-comp.c
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* Routines for decompression of PPP Van Jacobson compression
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* RFC 1144
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*
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* Wireshark - Network traffic analyzer
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* By Gerald Combs <gerald@wireshark.org>
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*
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* SPDX-License-Identifier: GPL-2.0-or-later
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*/
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/* The routines in this file were created by reading the description of
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* RFC 1144 available here: ftp://ftp.rfc-editor.org/in-notes/rfc1144.pdf
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* ONLY the description of the protocol in section 3.2 was used.
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* Notably, the sample implementation in Appendix A was NOT read by this file's
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* author, due to the questionable legality of using it in Wireshark.
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* For details on this issue, see:
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* https://gitlab.com/wireshark/wireshark/-/issues/12138
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*/
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/* Currently hard-coded to assume TCP over IPv4.
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* Nothing in the standard explicitly prevents an IPv6 implementation...
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*/
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#include "config.h"
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#include <glib.h>
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#include <epan/tvbuff.h>
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#include <epan/conversation.h>
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#include <epan/in_cksum.h>
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#include <epan/proto.h>
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#include <epan/expert.h>
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#include <epan/packet.h>
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#include <epan/ipproto.h>
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#include <epan/ppptypes.h>
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#include <wsutil/str_util.h>
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#include "packet-ip.h"
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#include "packet-ppp.h"
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/* Shorthand macros for reading/writing 16/32 bit values from
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* possibly-unaligned indexes into a guint8[]
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*/
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#define GET_16(p,i) (guint16)(((p)[(i)] << 8) | ((p)[(i)+1]))
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#define GET_32(p,i) (guint32)(((p)[(i)] << 24) | ((p)[(i)+1] << 16) | ((p)[(i)+2] << 8) | ((p)[(i)+3]))
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#define PUT_16(p,i,v) G_STMT_START { \
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(p)[(i)] = ((v) & 0xFF00) >> 8; \
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(p)[(i)+1] = ((v) & 0x00FF); \
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} G_STMT_END
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#define PUT_32(p,i,v) G_STMT_START { \
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(p)[(i)] = ((v) & 0xFF000000) >> 24; \
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(p)[(i)+1] = ((v) & 0x00FF0000) >> 16; \
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(p)[(i)+2] = ((v) & 0x0000FF00) >> 8; \
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(p)[(i)+3] = ((v) & 0x000000FF); \
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} G_STMT_END
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/* Store the last connection number we've seen.
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* Only used on the first pass, in case the connection number itself
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* gets compressed out.
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*/
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#define CNUM_INVALID G_MAXUINT16
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static guint16 last_cnum = CNUM_INVALID;
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/* Location in an IPv4 packet of the IP Next Protocol field
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* (which VJC replaces with the connection ID in uncompressed packets)
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*/
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#define VJC_CONNID_OFFSET 9
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/* Minimum TCP header length. We get compression data from the TCP header,
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* and also store it for future use.
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*/
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#define VJC_TCP_HDR_LEN 20
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/* Structure for tracking the changeable parts of a packet header */
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typedef struct vjc_hdr_s {
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guint16 tcp_chksum;
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guint16 urg;
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guint16 win;
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guint32 seq;
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guint32 ack;
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guint32 ip_id;
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gboolean psh;
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} vjc_hdr_t;
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/* The structure used in a wireshark "conversation" */
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typedef struct vjc_conv_s {
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guint32 last_frame; // On first pass, where to get the previous info
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guint32 last_frame_len; // On first pass, length of prev. frame (for SAWU/SWU)
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guint8 *frame_headers; // Full copy of the IP header
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guint8 header_len; // Length of the stored IP header
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wmem_map_t *vals; // Hash of frame_number => vjc_hdr_t*
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} vjc_conv_t;
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static dissector_handle_t ip_handle;
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void proto_register_vjc(void);
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void proto_reg_handoff_vjc(void);
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static int proto_vjc = -1;
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static gint ett_vjc = -1;
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static gint ett_vjc_change_mask = -1;
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static expert_field ei_vjc_sawu = EI_INIT;
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static expert_field ei_vjc_swu = EI_INIT;
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static expert_field ei_vjc_no_cnum = EI_INIT;
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static expert_field ei_vjc_no_conversation = EI_INIT;
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static expert_field ei_vjc_no_direction = EI_INIT;
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static expert_field ei_vjc_no_conv_data = EI_INIT;
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static expert_field ei_vjc_undecoded = EI_INIT;
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static expert_field ei_vjc_bad_data = EI_INIT;
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static expert_field ei_vjc_error = EI_INIT;
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#define VJC_FLAG_R 0x80
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#define VJC_FLAG_C 0x40
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#define VJC_FLAG_I 0x20
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#define VJC_FLAG_P 0x10
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#define VJC_FLAG_S 0x08
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#define VJC_FLAG_A 0x04
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#define VJC_FLAG_W 0x02
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#define VJC_FLAG_U 0x01
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#define VJC_FLAGS_SAWU 0x0F
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#define VJC_FLAGS_SWU 0x0B
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static int hf_vjc_comp = -1;
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static int hf_vjc_cnum = -1;
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static int hf_vjc_change_mask = -1;
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static int hf_vjc_change_mask_r = -1;
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static int hf_vjc_change_mask_c = -1;
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static int hf_vjc_change_mask_i = -1;
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static int hf_vjc_change_mask_p = -1;
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static int hf_vjc_change_mask_s = -1;
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static int hf_vjc_change_mask_a = -1;
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static int hf_vjc_change_mask_w = -1;
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static int hf_vjc_change_mask_u = -1;
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static int hf_vjc_chksum = -1;
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static int hf_vjc_urg = -1;
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static int hf_vjc_d_win = -1;
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static int hf_vjc_d_ack = -1;
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static int hf_vjc_d_seq = -1;
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static int hf_vjc_d_ipid = -1;
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static int hf_vjc_tcpdata = -1;
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static int * const vjc_change_mask_fields[] = {
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&hf_vjc_change_mask_r,
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&hf_vjc_change_mask_c,
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&hf_vjc_change_mask_i,
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&hf_vjc_change_mask_p,
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&hf_vjc_change_mask_s,
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&hf_vjc_change_mask_a,
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&hf_vjc_change_mask_w,
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&hf_vjc_change_mask_u,
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NULL
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};
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/* Initialization routine. Called at start of dissection.
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* Registered in proto_register_vjc() below.
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*/
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static void
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vjc_init_protocol(void)
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{
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last_cnum = CNUM_INVALID;
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}
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/* Cleanup routine. Called at close of file.
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* Registered in proto_register_vjc() below.
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*/
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static void
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vjc_cleanup_protocol(void)
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{
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last_cnum = CNUM_INVALID;
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}
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/* Find (or optionally create) a VJC conversation. */
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static conversation_t *
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vjc_find_conversation(packet_info *pinfo, guint32 vjc_cnum, gboolean create)
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{
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/* PPP gives us almost nothing to hook a conversation on; just whether
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* the packet is considered to be P2P_DIR_RECV or P2P_DIR_SENT.
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* Ideally we should also be distinguishing conversations based on the
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* capture interface, VLAN ID, MPLS tags, etc., etc. but that's beyond
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* the scope of this dissector, and a perennial problem in Wireshark anyway.
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* See <https://gitlab.com/wireshark/wireshark/-/issues/4561>
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*/
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conversation_t *conv = (conversation_t *)NULL;
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switch (pinfo->p2p_dir) {
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case P2P_DIR_RECV:
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vjc_cnum |= 0x0100;
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break;
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case P2P_DIR_SENT:
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vjc_cnum |= 0x0200;
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break;
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default:
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return conv;
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}
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conv = find_conversation_by_id(pinfo->num, CONVERSATION_NONE, vjc_cnum);
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if (!conv && create) {
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conv = conversation_new_by_id(pinfo->num, CONVERSATION_NONE, vjc_cnum);
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}
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return conv;
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}
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/* RFC 1144 section 3.2.2 says that "deltas" are sent for many values in the
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* header. If the initial byte is 0, that means the following 2 bytes are the
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* 16-bit value of the delta. Otherwise, the initial byte is the 8-bit value.
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*/
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static guint32
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vjc_delta_uint(proto_tree *tree, int hf, tvbuff_t *tvb, guint *offset)
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{
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guint32 ret_val;
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if (0 != tvb_get_guint8(tvb, *offset)) {
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proto_tree_add_item_ret_uint(tree, hf, tvb, *offset, 1,
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ENC_BIG_ENDIAN, &ret_val);
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(*offset)++;
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}
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else {
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(*offset)++;
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proto_tree_add_item_ret_uint(tree, hf, tvb, *offset, 2,
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ENC_BIG_ENDIAN, &ret_val);
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*offset += 2;
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}
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return ret_val;
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}
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/* Same thing but signed, since the TCP window delta can be negative */
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static gint32
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vjc_delta_int(proto_tree *tree, int hf, tvbuff_t *tvb, guint *offset)
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{
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gint32 ret_val;
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if (0 != tvb_get_gint8(tvb, *offset)) {
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proto_tree_add_item_ret_int(tree, hf, tvb, *offset, 1,
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ENC_BIG_ENDIAN, &ret_val);
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(*offset)++;
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}
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else {
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(*offset)++;
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proto_tree_add_item_ret_int(tree, hf, tvb, *offset, 2,
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ENC_BIG_ENDIAN, &ret_val);
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*offset += 2;
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}
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return ret_val;
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}
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/* Main dissection routine for uncompressed VJC packets.
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* Registered in proto_reg_handoff_vjc() below.
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*/
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static int
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dissect_vjc_uncomp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data)
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{
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/* A Van Jacobson uncompressed packet contains a standard TCP/IP header, with
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* the IP next protocol ID replaced with the connection number.
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* It's meant to signify a new TCP connection, or refresh an existing one,
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* which will have subsequent compressed packets.
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*/
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proto_tree *subtree = NULL;
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proto_item *ti = NULL;
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guint8 ip_ver = 0;
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guint8 ip_len = 0;
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guint tcp_len = 0;
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guint32 vjc_cnum = 0;
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tvbuff_t *tcpip_tvb = NULL;
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tvbuff_t *sub_tvb = NULL;
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conversation_t *conv = NULL;
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vjc_hdr_t *this_hdr = NULL;
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vjc_conv_t *pkt_data = NULL;
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guint8 *pdata = NULL;
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static guint8 real_proto = IP_PROTO_TCP;
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ti = proto_tree_add_item(tree, proto_vjc, tvb, 0, -1, ENC_NA);
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subtree = proto_item_add_subtree(ti, ett_vjc);
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proto_item_set_text(subtree, "PPP Van Jacobson uncompressed TCP/IP");
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/* Start with some sanity checks */
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if (VJC_CONNID_OFFSET+1 > tvb_captured_length(tvb)) {
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proto_tree_add_expert_format(subtree, pinfo, &ei_vjc_bad_data, tvb, 0, -1,
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"Packet truncated before Connection ID field");
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return tvb_captured_length(tvb);
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}
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ip_ver = (tvb_get_guint8(tvb, 0) & 0xF0) >> 4;
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ip_len = (tvb_get_guint8(tvb, 0) & 0x0F) << 2;
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tcp_len = ip_len + VJC_TCP_HDR_LEN;
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if (4 != ip_ver) {
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proto_tree_add_expert_format(subtree, pinfo, &ei_vjc_bad_data, tvb, 0, 1,
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"IPv%d unsupported for VJC compression", ip_ver);
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return tvb_captured_length(tvb);
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}
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/* So far so good, continue the dissection */
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ti = proto_tree_add_boolean(subtree, hf_vjc_comp, tvb, 0, 0, FALSE);
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proto_item_set_generated(ti);
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proto_tree_add_item_ret_uint(subtree, hf_vjc_cnum, tvb, VJC_CONNID_OFFSET, 1,
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ENC_BIG_ENDIAN, &vjc_cnum);
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/* Build a composite TVB containing the original TCP/IP data.
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* This is easy for uncompressed VJC packets because only one byte
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* is different from the on-the-wire data.
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*/
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sub_tvb = tvb_new_child_real_data(tvb, &real_proto, 1, 1);
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tvb_set_free_cb(sub_tvb, NULL);
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tcpip_tvb = tvb_new_composite();
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tvb_composite_append(tcpip_tvb, tvb_new_subset_length(tvb, 0, VJC_CONNID_OFFSET));
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tvb_composite_append(tcpip_tvb, sub_tvb);
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if (0 < tvb_captured_length_remaining(tvb, VJC_CONNID_OFFSET+1)) {
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tvb_composite_append(tcpip_tvb, tvb_new_subset_length(tvb, VJC_CONNID_OFFSET+1, -1));
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}
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tvb_composite_finalize(tcpip_tvb);
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add_new_data_source(pinfo, tcpip_tvb, "Original TCP/IP data");
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if (!(pinfo->p2p_dir == P2P_DIR_RECV || pinfo->p2p_dir == P2P_DIR_SENT)) {
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/* We can't make a proper conversation if we don't know the endpoints */
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proto_tree_add_expert(subtree, pinfo, &ei_vjc_no_direction, tvb, 0, 0);
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}
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else if (tcp_len > tvb_captured_length(tvb)) {
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/* Not enough data. We can still pass this packet onward (though probably
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* to no benefit), but can't base future decompression off of it.
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*/
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proto_tree_add_expert_format(subtree, pinfo, &ei_vjc_bad_data, tvb, 0, -1,
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"Packet truncated before end of TCP/IP headers");
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}
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else if (!pinfo->fd->visited) {
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/* If this is our first time visiting this packet, set things up for
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* decompressing future packets.
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*/
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last_cnum = vjc_cnum;
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conv = vjc_find_conversation(pinfo, vjc_cnum, TRUE);
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pkt_data = (vjc_conv_t *)conversation_get_proto_data(conv, proto_vjc);
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if (NULL == pkt_data) {
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pkt_data = wmem_new0(wmem_file_scope(), vjc_conv_t);
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pkt_data->vals = wmem_map_new(wmem_file_scope(), g_direct_hash, g_direct_equal);
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conversation_add_proto_data(conv, proto_vjc, (void *)pkt_data);
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}
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pdata = // shorthand
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pkt_data->frame_headers =
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(guint8 *)tvb_memdup(wmem_file_scope(), tcpip_tvb, 0, tcp_len);
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pkt_data->last_frame = pinfo->num;
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pkt_data->header_len = tcp_len;
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// This value is used for re-calculating seq/ack numbers
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pkt_data->last_frame_len = tvb_reported_length(tvb) - ip_len;
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this_hdr = wmem_new0(wmem_file_scope(), vjc_hdr_t);
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this_hdr->ip_id = GET_16(pdata, 4);
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this_hdr->seq = GET_32(pdata, ip_len + 4);
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this_hdr->ack = GET_32(pdata, ip_len + 8);
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this_hdr->psh = (pdata[ip_len + 13] & 0x08) == 0x08;
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this_hdr->win = GET_16(pdata, ip_len + 14);
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this_hdr->tcp_chksum = GET_16(pdata, ip_len + 16);
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this_hdr->urg = GET_16(pdata, ip_len + 18);
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wmem_map_insert(pkt_data->vals, GUINT_TO_POINTER(pinfo->num), this_hdr);
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}
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else {
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/* We've already visited this packet, we should have all the info we need. */
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}
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return call_dissector_with_data(ip_handle, tcpip_tvb, pinfo, tree, data);
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}
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/* Main dissection routine for compressed VJC packets.
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* Registered in proto_reg_handoff_vjc() below.
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*/
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static int
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dissect_vjc_comp(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree, void* data _U_)
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{
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/* A Van Jacobson compressed packet contains a change mask, which indicates
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* possible fields that may be present.
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*/
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proto_tree *subtree = NULL;
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proto_item *ti = NULL;
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guint hdr_len = 3; // See below
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gboolean hdr_error = FALSE;
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guint ip_len = 0;
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guint pkt_len = 0;
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guint d_ipid = 0;
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guint d_seq = 0;
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guint d_ack = 0;
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gint d_win = 0;
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guint8 flags = 0;
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guint offset = 0;
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guint32 urg = 0;
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guint32 ip_chksum = 0;
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guint32 tcp_chksum = 0;
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guint32 vjc_cnum = 0;
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conversation_t *conv = NULL;
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vjc_hdr_t *this_hdr = NULL;
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vjc_hdr_t *last_hdr = NULL;
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vjc_conv_t *pkt_data = NULL;
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guint8 *pdata = NULL;
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tvbuff_t *tcpip_tvb = NULL;
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tvbuff_t *sub_tvb = NULL;
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/* Calculate the length of the VJC header,
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* accounting for extensions in the delta fields.
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* We start with a value of 3, because we'll always have
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* an 8-bit change mask and a 16-bit TCP checksum.
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*/
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#define TEST_HDR_LEN \
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if (hdr_len > tvb_captured_length(tvb)) { hdr_error = TRUE; goto done_header_len; }
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TEST_HDR_LEN;
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flags = tvb_get_guint8(tvb, offset);
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if (flags & VJC_FLAG_C) {
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// have connection number
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hdr_len++;
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TEST_HDR_LEN;
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}
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if ((flags & VJC_FLAGS_SAWU) == VJC_FLAGS_SAWU) {
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/* Special case for "unidirectional data transfer".
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* No change to header size; d_ack = 0, and
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* we're to calculate d_seq ourselves.
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*/
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}
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else if ((flags & VJC_FLAGS_SAWU) == VJC_FLAGS_SWU) {
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/* Special case for "echoed interactive traffic".
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* No change to header size; we're to calculate d_seq and d_ack.
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*/
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}
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else {
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/* Not a special case, determine the header size by
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* testing the SAWU flags individually.
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*/
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if (flags & VJC_FLAG_U) {
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// have urgent pointer
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hdr_len += 2;
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TEST_HDR_LEN;
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}
|
||
if (flags & VJC_FLAG_W) {
|
||
// have d_win
|
||
if (0 == tvb_get_gint8(tvb, offset + hdr_len))
|
||
hdr_len += 3;
|
||
else
|
||
hdr_len++;
|
||
TEST_HDR_LEN;
|
||
}
|
||
if (flags & VJC_FLAG_A) {
|
||
// have d_ack
|
||
if (0 == tvb_get_guint8(tvb, offset + hdr_len))
|
||
hdr_len += 3;
|
||
else
|
||
hdr_len++;
|
||
TEST_HDR_LEN;
|
||
}
|
||
if (flags & VJC_FLAG_S) {
|
||
// have d_seq
|
||
if (0 == tvb_get_guint8(tvb, offset + hdr_len))
|
||
hdr_len += 3;
|
||
else
|
||
hdr_len++;
|
||
TEST_HDR_LEN;
|
||
}
|
||
}
|
||
if (flags & VJC_FLAG_I) {
|
||
// have IP ID
|
||
if (0 == tvb_get_guint8(tvb, offset + hdr_len))
|
||
hdr_len += 3;
|
||
else
|
||
hdr_len++;
|
||
TEST_HDR_LEN;
|
||
}
|
||
|
||
/* Now that we have the header length, use it when assigning the
|
||
* protocol item.
|
||
*/
|
||
#undef TEST_HDR_LEN
|
||
done_header_len:
|
||
ti = proto_tree_add_item(tree, proto_vjc, tvb, 0,
|
||
MIN(hdr_len, tvb_captured_length(tvb)), ENC_NA);
|
||
subtree = proto_item_add_subtree(ti, ett_vjc);
|
||
proto_item_set_text(subtree, "PPP Van Jacobson compressed TCP/IP");
|
||
if (hdr_error) {
|
||
proto_tree_add_expert_format(subtree, pinfo, &ei_vjc_bad_data, tvb, 0, -1,
|
||
"Packet truncated, compression header incomplete");
|
||
return tvb_captured_length(tvb);
|
||
}
|
||
|
||
ti = proto_tree_add_boolean(subtree, hf_vjc_comp, tvb, 0, 0, TRUE);
|
||
proto_item_set_generated(ti);
|
||
|
||
proto_tree_add_bitmask(subtree, tvb, 0, hf_vjc_change_mask,
|
||
ett_vjc_change_mask, vjc_change_mask_fields, ENC_NA);
|
||
if ((flags & VJC_FLAGS_SAWU) == VJC_FLAGS_SAWU) {
|
||
proto_tree_add_expert(subtree, pinfo, &ei_vjc_sawu, tvb, 0, 1);
|
||
}
|
||
else if ((flags & VJC_FLAGS_SAWU) == VJC_FLAGS_SWU) {
|
||
proto_tree_add_expert(subtree, pinfo, &ei_vjc_swu, tvb, 0, 1);
|
||
}
|
||
|
||
offset++;
|
||
|
||
if (flags & VJC_FLAG_C) {
|
||
proto_tree_add_item_ret_uint(subtree, hf_vjc_cnum, tvb, offset, 1,
|
||
ENC_BIG_ENDIAN, &vjc_cnum);
|
||
last_cnum = vjc_cnum;
|
||
offset++;
|
||
}
|
||
else {
|
||
vjc_cnum = last_cnum;
|
||
if (vjc_cnum != CNUM_INVALID) {
|
||
ti = proto_tree_add_uint(subtree, hf_vjc_cnum, tvb, offset, 0, vjc_cnum);
|
||
proto_item_set_generated(ti);
|
||
}
|
||
else {
|
||
proto_tree_add_expert(subtree, pinfo, &ei_vjc_no_cnum, tvb, 0, 0);
|
||
}
|
||
}
|
||
conv = vjc_find_conversation(pinfo, vjc_cnum, FALSE);
|
||
if (NULL != conv) {
|
||
pkt_data = (vjc_conv_t *)conversation_get_proto_data(conv, proto_vjc);
|
||
// Will be testing that pkt_data exists below
|
||
}
|
||
else {
|
||
proto_tree_add_expert(subtree, pinfo, &ei_vjc_no_conversation,
|
||
tvb, 1, (flags & VJC_FLAG_C) ? 1 : 0);
|
||
}
|
||
|
||
proto_tree_add_item_ret_uint(subtree, hf_vjc_chksum, tvb, offset, 2,
|
||
ENC_BIG_ENDIAN, &tcp_chksum);
|
||
offset += 2;
|
||
|
||
if ((flags & VJC_FLAGS_SAWU) == VJC_FLAGS_SAWU) {
|
||
/* Special case for "unidirectional data transfer".
|
||
* d_ack is 0, and d_seq changed by the amount of data in the previous packet.
|
||
*/
|
||
flags &= ~VJC_FLAGS_SAWU;
|
||
d_ack = 0;
|
||
if (NULL != pkt_data) {
|
||
d_seq = pkt_data->last_frame_len;
|
||
}
|
||
ti = proto_tree_add_uint(subtree, hf_vjc_d_ack, tvb, offset, 0, d_ack);
|
||
proto_item_set_generated(ti);
|
||
ti = proto_tree_add_uint(subtree, hf_vjc_d_seq, tvb, offset, 0, d_seq);
|
||
proto_item_set_generated(ti);
|
||
}
|
||
else if ((flags & VJC_FLAGS_SAWU) == VJC_FLAGS_SWU) {
|
||
/* Special case for "echoed interactive traffic".
|
||
* d_seq and d_ack changed by the amount of user data in the
|
||
* previous packet.
|
||
*/
|
||
flags &= ~VJC_FLAGS_SAWU;
|
||
if (NULL != pkt_data) {
|
||
d_seq = d_ack = pkt_data->last_frame_len;
|
||
}
|
||
ti = proto_tree_add_uint(subtree, hf_vjc_d_ack, tvb, offset, 0, d_ack);
|
||
proto_item_set_generated(ti);
|
||
ti = proto_tree_add_uint(subtree, hf_vjc_d_seq, tvb, offset, 0, d_seq);
|
||
proto_item_set_generated(ti);
|
||
}
|
||
else {
|
||
/* Not a special case, read the SAWU flags individually */
|
||
|
||
if (flags & VJC_FLAG_U) {
|
||
/* "The packet’s urgent pointer is sent if URG is set ..."
|
||
* I assume that means the full 16-bit value here.
|
||
*/
|
||
proto_tree_add_item_ret_uint(subtree, hf_vjc_urg, tvb, offset, 2,
|
||
ENC_BIG_ENDIAN, &urg);
|
||
offset += 2;
|
||
}
|
||
else {
|
||
urg = 0;
|
||
}
|
||
|
||
if (flags & VJC_FLAG_W) {
|
||
/* "The number sent for the window is also the difference between the current
|
||
* and previous values. However, either positive or negative changes are
|
||
* allowed since the window is a 16-bit field."
|
||
*/
|
||
d_win = vjc_delta_int(subtree, hf_vjc_d_win, tvb, &offset);
|
||
}
|
||
else {
|
||
d_win = 0;
|
||
}
|
||
|
||
/* The rest of the deltas can only be positive. */
|
||
if (flags & VJC_FLAG_A) {
|
||
d_ack = vjc_delta_uint(subtree, hf_vjc_d_ack, tvb, &offset);
|
||
}
|
||
else {
|
||
d_ack = 0;
|
||
}
|
||
|
||
if (flags & VJC_FLAG_S) {
|
||
d_seq = vjc_delta_uint(subtree, hf_vjc_d_seq, tvb, &offset);
|
||
}
|
||
else {
|
||
d_seq = 0;
|
||
}
|
||
}
|
||
|
||
if (flags & VJC_FLAG_I) {
|
||
d_ipid = vjc_delta_uint(subtree, hf_vjc_d_ipid, tvb, &offset);
|
||
}
|
||
else {
|
||
/* "However, unlike the rest of the compressed fields, the assumed
|
||
* change when I is clear is one, not zero." - section 3.2.2
|
||
*/
|
||
d_ipid = 1;
|
||
ti = proto_tree_add_uint(subtree, hf_vjc_d_ipid, tvb, offset, 0, d_ipid);
|
||
proto_item_set_generated(ti);
|
||
}
|
||
|
||
if (!(pinfo->p2p_dir == P2P_DIR_RECV || pinfo->p2p_dir == P2P_DIR_SENT)) {
|
||
/* We can't make a proper conversation if we don't know the endpoints */
|
||
proto_tree_add_expert(subtree, pinfo, &ei_vjc_no_direction, tvb, offset,
|
||
tvb_captured_length_remaining(tvb, offset));
|
||
return tvb_captured_length(tvb);
|
||
}
|
||
if (NULL == conv) {
|
||
proto_tree_add_expert(subtree, pinfo, &ei_vjc_undecoded, tvb, offset,
|
||
tvb_captured_length_remaining(tvb, offset));
|
||
return tvb_captured_length(tvb);
|
||
}
|
||
if (NULL == pkt_data) {
|
||
proto_tree_add_expert(subtree, pinfo, &ei_vjc_no_conv_data, tvb, offset,
|
||
tvb_captured_length_remaining(tvb, offset));
|
||
return tvb_captured_length(tvb);
|
||
}
|
||
|
||
if (!pinfo->fd->visited) {
|
||
/* We haven't visited this packet before.
|
||
* Form its vjc_hdr_t from the deltas and the info from the previous frame.
|
||
*/
|
||
last_hdr = (vjc_hdr_t *)wmem_map_lookup(pkt_data->vals,
|
||
GUINT_TO_POINTER(pkt_data->last_frame));
|
||
|
||
if (NULL != last_hdr) {
|
||
this_hdr = wmem_new0(wmem_file_scope(), vjc_hdr_t);
|
||
this_hdr->tcp_chksum = (guint16)tcp_chksum;
|
||
this_hdr->urg = (guint16)urg;
|
||
this_hdr->win = last_hdr->win + d_win;
|
||
this_hdr->seq = last_hdr->seq + d_seq;
|
||
this_hdr->ack = last_hdr->ack + d_ack;
|
||
this_hdr->ip_id = last_hdr->ip_id + d_ipid;
|
||
this_hdr->psh = (flags & VJC_FLAG_P) == VJC_FLAG_P;
|
||
wmem_map_insert(pkt_data->vals, GUINT_TO_POINTER(pinfo->num), this_hdr);
|
||
|
||
// This frame is the next frame's last frame
|
||
pkt_data->last_frame = pinfo->num;
|
||
pkt_data->last_frame_len = tvb_reported_length_remaining(tvb, offset);
|
||
}
|
||
else {
|
||
proto_tree_add_expert_format(subtree, pinfo, &ei_vjc_error, tvb, 0, 0,
|
||
"Dissector error: unable to find headers for prior frame %d",
|
||
pkt_data->last_frame);
|
||
return tvb_captured_length(tvb);
|
||
}
|
||
// if last_hdr is null, then this_hdr will stay null and be handled below
|
||
}
|
||
else {
|
||
/* We have visited this packet before.
|
||
* Get the values we saved the first time.
|
||
*/
|
||
this_hdr = (vjc_hdr_t *)wmem_map_lookup(pkt_data->vals,
|
||
GUINT_TO_POINTER(pinfo->num));
|
||
}
|
||
if (NULL != this_hdr) {
|
||
/* pkt_data->frame_headers is our template packet header data.
|
||
* Apply changes to it as needed.
|
||
* The changes are intentionally done in the template before copying.
|
||
*/
|
||
pkt_len = pkt_data->header_len + tvb_reported_length_remaining(tvb, offset);
|
||
|
||
pdata = pkt_data->frame_headers; /* shorthand */
|
||
ip_len = (pdata[0] & 0x0F) << 2;
|
||
|
||
/* IP length */
|
||
PUT_16(pdata, 2, pkt_len);
|
||
|
||
/* IP ID */
|
||
PUT_16(pdata, 4, this_hdr->ip_id);
|
||
|
||
/* IP checksum */
|
||
PUT_16(pdata, 10, 0x0000);
|
||
ip_chksum = ip_checksum(pdata, ip_len);
|
||
PUT_16(pdata, 10, g_htons(ip_chksum));
|
||
|
||
/* TCP seq */
|
||
PUT_32(pdata, ip_len + 4, this_hdr->seq);
|
||
|
||
/* TCP ack */
|
||
PUT_32(pdata, ip_len + 8, this_hdr->ack);
|
||
|
||
/* TCP window */
|
||
PUT_16(pdata, ip_len + 14, this_hdr->win);
|
||
|
||
/* TCP push */
|
||
if (this_hdr->psh) {
|
||
pdata[ip_len + 13] |= 0x08;
|
||
}
|
||
else {
|
||
pdata[ip_len + 13] &= ~0x08;
|
||
}
|
||
|
||
/* TCP checksum */
|
||
PUT_16(pdata, ip_len + 16, this_hdr->tcp_chksum);
|
||
|
||
/* TCP urg */
|
||
if (this_hdr->urg) {
|
||
pdata[ip_len + 13] |= 0x20;
|
||
PUT_16(pdata, ip_len + 18, this_hdr->urg);
|
||
}
|
||
else {
|
||
pdata[ip_len + 13] &= ~0x20;
|
||
PUT_16(pdata, ip_len + 18, 0x0000);
|
||
}
|
||
|
||
/* Now that we're done manipulating the packet header, stick it into
|
||
* a TVB for sub-dissectors to use.
|
||
*/
|
||
sub_tvb = tvb_new_child_real_data(tvb, pdata,
|
||
pkt_data->header_len, pkt_data->header_len);
|
||
tvb_set_free_cb(sub_tvb, NULL);
|
||
|
||
// Reuse pkt_len
|
||
pkt_len = tvb_captured_length_remaining(tvb, offset);
|
||
if (0 < pkt_len) {
|
||
tcpip_tvb = tvb_new_composite();
|
||
tvb_composite_append(tcpip_tvb, sub_tvb);
|
||
tvb_composite_append(tcpip_tvb, tvb_new_subset_remaining(tvb, offset));
|
||
tvb_composite_finalize(tcpip_tvb);
|
||
|
||
ti = proto_tree_add_item(subtree, hf_vjc_tcpdata, tvb, offset, pkt_len, ENC_NA);
|
||
proto_item_set_text(ti, "TCP data (%d byte%s)", pkt_len, plurality(pkt_len, "", "s"));
|
||
}
|
||
else
|
||
{
|
||
tcpip_tvb = sub_tvb;
|
||
}
|
||
|
||
add_new_data_source(pinfo, tcpip_tvb, "Decompressed TCP/IP data");
|
||
return offset + call_dissector_with_data(ip_handle, tcpip_tvb, pinfo, tree, data);
|
||
}
|
||
else {
|
||
proto_tree_add_expert_format(subtree, pinfo, &ei_vjc_error, tvb, 0, 0,
|
||
"Dissector error: unable to find headers for current frame %d",
|
||
pinfo->num);
|
||
}
|
||
return tvb_captured_length(tvb);
|
||
}
|
||
|
||
void
|
||
proto_register_vjc(void)
|
||
{
|
||
static hf_register_info hf[] = {
|
||
{ &hf_vjc_comp,
|
||
{ "Is compressed", "vjc.compressed", FT_BOOLEAN, BASE_NONE,
|
||
NULL, 0x0, NULL, HFILL }},
|
||
{ &hf_vjc_cnum,
|
||
{ "Connection number", "vjc.connection_number", FT_UINT8, BASE_DEC,
|
||
NULL, 0x0, NULL, HFILL }},
|
||
{ &hf_vjc_change_mask,
|
||
{ "Change mask", "vjc.change_mask", FT_UINT8, BASE_HEX,
|
||
NULL, 0x0, NULL, HFILL }},
|
||
{ &hf_vjc_change_mask_r,
|
||
{ "Reserved", "vjc.change_mask.reserved", FT_BOOLEAN, 8,
|
||
TFS(&tfs_set_notset), VJC_FLAG_R, "Undefined bit", HFILL }},
|
||
{ &hf_vjc_change_mask_c,
|
||
{ "Connection number flag", "vjc.change_mask.connection_number", FT_BOOLEAN, 8,
|
||
TFS(&tfs_set_notset), VJC_FLAG_C, "Whether connection number is present", HFILL }},
|
||
{ &hf_vjc_change_mask_i,
|
||
{ "IP ID flag", "vjc.change_mask.ip_id", FT_BOOLEAN, 8,
|
||
TFS(&tfs_set_notset), VJC_FLAG_I, "Whether IP ID is present", HFILL }},
|
||
{ &hf_vjc_change_mask_p,
|
||
{ "TCP PSH flag", "vjc.change_mask.psh", FT_BOOLEAN, 8,
|
||
TFS(&tfs_set_notset), VJC_FLAG_P, "Whether to set TCP PSH", HFILL }},
|
||
{ &hf_vjc_change_mask_s,
|
||
{ "TCP Sequence flag", "vjc.change_mask.seq", FT_BOOLEAN, 8,
|
||
TFS(&tfs_set_notset), VJC_FLAG_S, "Whether TCP SEQ is present", HFILL }},
|
||
{ &hf_vjc_change_mask_a,
|
||
{ "TCP Acknowledgement flag", "vjc.change_mask.ack", FT_BOOLEAN, 8,
|
||
TFS(&tfs_set_notset), VJC_FLAG_A, "Whether TCP ACK is present", HFILL }},
|
||
{ &hf_vjc_change_mask_w,
|
||
{ "TCP Window flag", "vjc.change_mask.win", FT_BOOLEAN, 8,
|
||
TFS(&tfs_set_notset), VJC_FLAG_W, "Whether TCP Window is present", HFILL }},
|
||
{ &hf_vjc_change_mask_u,
|
||
{ "TCP Urgent flag", "vjc.change_mask.urg", FT_BOOLEAN, 8,
|
||
TFS(&tfs_set_notset), VJC_FLAG_U, "Whether TCP URG pointer is present", HFILL }},
|
||
{ &hf_vjc_chksum,
|
||
{ "TCP Checksum", "vjc.checksum", FT_UINT16, BASE_HEX,
|
||
NULL, 0x0, "TCP checksum of original packet", HFILL}},
|
||
{ &hf_vjc_urg,
|
||
{ "Urgent pointer", "vjc.urgent_pointer", FT_UINT16, BASE_DEC,
|
||
NULL, 0x0, "TCP urgent pointer of original packet", HFILL}},
|
||
{ &hf_vjc_d_win,
|
||
{ "Delta window", "vjc.delta_window", FT_INT16, BASE_DEC,
|
||
NULL, 0x0, "Change in TCP window size from previous packet", HFILL}},
|
||
{ &hf_vjc_d_ack,
|
||
{ "Delta ack", "vjc.delta_ack", FT_UINT16, BASE_DEC,
|
||
NULL, 0x0, "Change in TCP acknowledgement number from previous packet", HFILL}},
|
||
{ &hf_vjc_d_seq,
|
||
{ "Delta seq", "vjc.delta_seq", FT_UINT16, BASE_DEC,
|
||
NULL, 0x0, "Change in TCP sequence number from previous packet", HFILL}},
|
||
{ &hf_vjc_d_ipid,
|
||
{ "Delta IP ID", "vjc.delta_ipid", FT_UINT16, BASE_DEC,
|
||
NULL, 0x0, "Change in IP Identification number from previous packet", HFILL}},
|
||
{ &hf_vjc_tcpdata,
|
||
{ "TCP data", "vjc.tcp_data", FT_BYTES, BASE_NONE,
|
||
NULL, 0x0, "Original TCP payload", HFILL}},
|
||
};
|
||
|
||
static gint *ett[] = {
|
||
&ett_vjc,
|
||
&ett_vjc_change_mask,
|
||
};
|
||
|
||
expert_module_t* expert_vjc;
|
||
static ei_register_info ei[] = {
|
||
{ &ei_vjc_sawu,
|
||
{ "vjc.special.sawu", PI_PROTOCOL, PI_CHAT,
|
||
".... 1111 = special case for \"unidirectional data transfer\"", EXPFILL }},
|
||
{ &ei_vjc_swu,
|
||
{ "vjc.special.swu", PI_PROTOCOL, PI_CHAT,
|
||
".... 1011 = special case for \"echoed interactive traffic\"", EXPFILL }},
|
||
{ &ei_vjc_no_cnum,
|
||
{ "vjc.no_connection_id", PI_PROTOCOL, PI_WARN,
|
||
"No connection ID and no prior connection (common at capture start)", EXPFILL }},
|
||
{ &ei_vjc_no_conversation,
|
||
{ "vjc.no_connection", PI_PROTOCOL, PI_WARN,
|
||
"No saved connection found (common at capture start)", EXPFILL }},
|
||
{ &ei_vjc_no_direction,
|
||
{ "vjc.no_direction", PI_UNDECODED, PI_WARN,
|
||
"Connection has no direction info, cannot decompress", EXPFILL }},
|
||
{ &ei_vjc_no_conv_data,
|
||
{ "vjc.no_connection_data", PI_UNDECODED, PI_WARN,
|
||
"Could not find saved connection data", EXPFILL }},
|
||
{ &ei_vjc_undecoded,
|
||
{ "vjc.no_decompress", PI_UNDECODED, PI_WARN,
|
||
"Undecoded data (impossible due to missing information)", EXPFILL }},
|
||
{ &ei_vjc_bad_data,
|
||
{ "vjc.bad_data", PI_PROTOCOL, PI_ERROR,
|
||
"Non-compliant packet data", EXPFILL }},
|
||
{ &ei_vjc_error,
|
||
{ "vjc.error", PI_MALFORMED, PI_ERROR,
|
||
"Unrecoverable dissector error", EXPFILL }},
|
||
};
|
||
|
||
proto_vjc = proto_register_protocol("Van Jacobson PPP compression", "VJC", "vjc");
|
||
proto_register_field_array(proto_vjc, hf, array_length(hf));
|
||
proto_register_subtree_array(ett, array_length(ett));
|
||
expert_vjc = expert_register_protocol(proto_vjc);
|
||
expert_register_field_array(expert_vjc, ei, array_length(ei));
|
||
|
||
register_init_routine(&vjc_init_protocol);
|
||
register_cleanup_routine(&vjc_cleanup_protocol);
|
||
}
|
||
|
||
void
|
||
proto_reg_handoff_vjc(void)
|
||
{
|
||
dissector_handle_t vjcu_handle;
|
||
dissector_handle_t vjcc_handle;
|
||
|
||
ip_handle = find_dissector("ip");
|
||
|
||
vjcc_handle = create_dissector_handle(dissect_vjc_comp, proto_vjc);
|
||
dissector_add_uint("ppp.protocol", PPP_VJC_COMP, vjcc_handle);
|
||
|
||
vjcu_handle = create_dissector_handle(dissect_vjc_uncomp, proto_vjc);
|
||
dissector_add_uint("ppp.protocol", PPP_VJC_UNCOMP, vjcu_handle);
|
||
}
|
||
|
||
/*
|
||
* Editor modelines - https://www.wireshark.org/tools/modelines.html
|
||
*
|
||
* Local variables:
|
||
* c-basic-offset: 4
|
||
* tab-width: 8
|
||
* indent-tabs-mode: nil
|
||
* End:
|
||
*
|
||
* vi: set shiftwidth=4 tabstop=8 expandtab:
|
||
* :indentSize=4:tabSize=8:noTabs=true:
|
||
*/
|