Wireshark · Ethereal-dev: Re: [ethereal-dev] unable to trace ppp on linux

[Guy Harris <gharris@xxxxxxxxxxxx>]

On Thu, Sep 07, 2000 at 12:12:57AM -0500, richard.coe@xxxxxxxxxx wrote:
>     Without diving into the code more, I don't know if it is easier/better
>     to fix this in libpcap or ethereal.  

It is by far better to fix it in Ethereal, which is why it'll be fixed
in the next release, and is also fixed by applying the attached patch to
Ethereal's "wiretap/libpcap.c" (said patch updating that file to the
version currently checked in).

Fixing it in libpcap means backing out changes in the 0.5[.x] libpcap
that attempt to work around the ********* *********** of differing
numerical values for the same DLT_ codes on different platforms.

Index: wiretap/libpcap.c
===================================================================
RCS file: /usr/local/cvsroot/ethereal/wiretap/libpcap.c,v
retrieving revision 1.37
retrieving revision 1.38
diff -c -r1.37 -r1.38
*** wiretap/libpcap.c	2000/07/30 16:54:11	1.37
--- wiretap/libpcap.c	2000/08/25 06:25:21	1.38
***************
*** 45,118 ****
      const union wtap_pseudo_header *pseudo_header, const u_char *pd, int *err);
  
  /*
!  * XXX - this is a bit of a mess.  OpenBSD, and perhaps NetBSD, and
!  * BSD/OS have different DLT_ codes from FreeBSD (and from the LBL
!  * BPF code), and, at least in some cases, from each other.
!  * For now, we simply treat those type values with different
!  * meanings on different platforms, except for DLT_RAW, as "unknown";
!  * this means you won't be able to capture from a network using those
!  * types in Ethereal (and that capturing from the loopback interface
!  * won't necessarily work right on OpenBSD, either, as it uses
!  * DLT_LOOP, which is the same as DLT_RAW on other platforms).
   *
!  * Does anybody know what BSD/OS uses as DLT_ types for SLIP and
!  * PPP?  The LBL code, and the OpenBSD code, appear to disagree....
   *
!  * Nothing in FreeBSD appears to use DLT_RAW, so it's not clear what
!  * link-layer header or fake header appears for DLT_RAW.  If it's
!  * completely unused, or if it behaves the same way OpenBSD DLT_LOOP
!  * behaves, i.e. it puts an address family in *network* byte order
!  * (as opposed to the *host* byte order that DLT_NULL uses on FreeBSD),
!  * then we should just make it WTAP_ENCAP_NULL, which we treat in
!  * such a fashion as to cause it to work with DLT_LOOP headers.
   */
! static const int pcap_encap[] = {
! 	WTAP_ENCAP_NULL,	/* null encapsulation */
! 	WTAP_ENCAP_ETHERNET,
! 	WTAP_ENCAP_UNKNOWN,	/* 3Mb experimental Ethernet */
! 	WTAP_ENCAP_UNKNOWN,	/* Amateur Radio AX.25 */
! 	WTAP_ENCAP_UNKNOWN,	/* Proteon ProNET Token Ring */
! 	WTAP_ENCAP_UNKNOWN,	/* Chaos */
! 	WTAP_ENCAP_TR,		/* IEEE 802 Networks - assume token ring */
! 	WTAP_ENCAP_ARCNET,
! 	WTAP_ENCAP_SLIP,
! 	WTAP_ENCAP_PPP,
  #ifdef BIT_SWAPPED_MAC_ADDRS
! 	WTAP_ENCAP_FDDI_BITSWAPPED,
  #else
! 	WTAP_ENCAP_FDDI,
  #endif
! 	WTAP_ENCAP_ATM_RFC1483,	/* or, on BSD/OS, Frame Relay */
! 	WTAP_ENCAP_RAW_IP,	/* or, on OpenBSD, DLT_LOOP, and on BSD/OS,
! 				   Cisco HDLC */
! 	WTAP_ENCAP_UNKNOWN,	/* In LBL BPF and FreeBSD, BSD/OS SLIP;
! 				   on OpenBSD, DLT_ENC; on BSD/OS,
! 				   DLT_ATM_RFC1483 */
! 	WTAP_ENCAP_UNKNOWN,	/* In LBL BPF and FreeBSD, BSD/OS PPP;
! 				   on OpenBSD and BSD/OS, DLT_RAW */
! 	WTAP_ENCAP_UNKNOWN,	/* In OpenBSD and BSD/OS, BSD/OS SLIP,
! 				   but the BSD/OS header says "internal
! 				   to libpcap", whatever that means;
! 				   in Linux with the ISDN4Linux patches
! 				   applied to libpcap, DLT_I4L_RAWIP,
! 				   which looks just like DLT_RAW but
! 				   is given a different DLT_ code for
! 				   no obvious good reason */
! 	WTAP_ENCAP_UNKNOWN,	/* In OpenBSD and BSD/OS, BSD/OS PPP,
! 				   but the BSD/OS header says "internal
! 				   to libpcap", whatever that means;
! 				   in Linux with the ISDN4Linux patches
! 				   applied to libpcap, DLT_I4L_IP,
! 				   which provides only a 2-octet
! 				   Ethernet type as a link-layer header,
! 				   with a type of 0xFFFF meaning
! 				   ETH_P_802_3, a "Dummy type for 802.3
! 				   frames" */
! 	WTAP_ENCAP_UNKNOWN,
! 	WTAP_ENCAP_UNKNOWN,
! 	WTAP_ENCAP_LINUX_ATM_CLIP
  };
! #define NUM_PCAP_ENCAPS (sizeof pcap_encap / sizeof pcap_encap[0])
  
  int libpcap_open(wtap *wth, int *err)
  {
--- 45,245 ----
      const union wtap_pseudo_header *pseudo_header, const u_char *pd, int *err);
  
  /*
!  * Either LBL NRG wasn't an adequate central registry (e.g., because of
!  * the slow rate of releases from them), or nobody bothered using them
!  * as a central registry, as many different groups have patched libpcap
!  * (and BPF, on the BSDs) to add new encapsulation types, and have ended
!  * up using the same DLT_ values for different encapsulation types.
   *
!  * For those numerical encapsulation type values that everybody uses for
!  * the same encapsulation type (which inclues those that some platforms
!  * specify different DLT_ names for but don't appear to use), we map
!  * those values to the appropriate Wiretap values.
   *
!  * For those numerical encapsulation type values that different libpcap
!  * variants use for different encapsulation types, we check what
!  * <pcap.h> defined to determine how to interpret them, so that we
!  * interpret them the way the libpcap with which we're building
!  * Ethereal/Wiretap interprets them (which, if it doesn't support
!  * them at all, means we don't support them either - any capture files
!  * using them are foreign, and we don't hazard a guess as to which
!  * platform they came from; we could, I guess, choose the most likely
!  * platform).
   */
! 
! #ifdef HAVE_PCAP_H
! #include <pcap.h>
! #endif
! 
! static const struct {
! 	int	dlt_value;
! 	int	wtap_encap_value;
! } pcap_to_wtap_map[] = {
! 	/*
! 	 * These are the values that are almost certainly the same
! 	 * in all libpcaps (I've yet to find one where the values
! 	 * in question are used for some purpose other than the
! 	 * one below, but...), and that Wiretap and Ethereal
! 	 * currently support.
! 	 */
! 	{ 0,		WTAP_ENCAP_NULL },	/* null encapsulation */
! 	{ 1,		WTAP_ENCAP_ETHERNET },
! 	{ 6,		WTAP_ENCAP_TR },	/* IEEE 802 Networks - assume token ring */
! 	{ 7,		WTAP_ENCAP_ARCNET },
! 	{ 8,		WTAP_ENCAP_SLIP },
! 	{ 9,		WTAP_ENCAP_PPP },
  #ifdef BIT_SWAPPED_MAC_ADDRS
! 	{ 10,		WTAP_ENCAP_FDDI_BITSWAPPED },
! #else
! 	{ 10,		WTAP_ENCAP_FDDI },
! #endif
! 
! 	/*
! 	 * 11 is DLT_ATM_RFC1483 on most platforms; the only libpcaps I've
! 	 * seen that define anything other than DLT_ATM_RFC1483 as 11 are
! 	 * the BSD/OS one, which defines DLT_FR as 11, and libpcap 0.5,
! 	 * which define it as 100, mapping the kernel's value to 100, in
! 	 * an attempt to hide the different values used on different
! 	 * platforms.
! 	 *
! 	 * If this is a platform where DLT_FR is defined as 11, we
! 	 * don't handle 11 at all; otherwise, we handle it as
! 	 * DLT_ATM_RFC1483 (this means we'd misinterpret Frame Relay
! 	 * captures from BSD/OS if running on platforms other than BSD/OS,
! 	 * but
! 	 *
! 	 *	1) we don't yet support DLT_FR
! 	 *
! 	 * and
! 	 *
! 	 *	2) nothing short of a heuristic would let us interpret
! 	 *	   them correctly).
! 	 */
! #if defined(DLT_FR) && (DLT_FR == 11)
! 	/* Put entry for Frame Relay here */
  #else
! 	{ 11,		WTAP_ENCAP_ATM_RFC1483 },
  #endif
! 
! 	/*
! 	 * 12 is DLT_RAW on most platforms, but it's DLT_C_HDLC on
! 	 * BSD/OS, and DLT_LOOP on OpenBSD.
! 	 *
! 	 * We don't yet handle DLT_C_HDLC, but we can handle DLT_LOOP
! 	 * (it's just like DLT_NULL, only with the AF_ value in network
! 	 * rather than host byte order - Ethereal figures out the
! 	 * byte order from the data, so we don't care what byte order
! 	 * it's in), so if DLT_LOOP is defined as 12, interpret 12
! 	 * as WTAP_ENCAP_NULL, otherwise, unless DLT_C_HDLC is defined
! 	 * as 12, interpret it as WTAP_ENCAP_RAW_IP.
! 	 */
! #if defined(DLT_LOOP) && (DLT_LOOP == 12)
! 	{ 12,		WTAP_ENCAP_NULL },
! #elif defined(DLT_C_HDLC) && (DLT_C_HDLC == 12)
! 	/* Put entry for Cisco HDLC here */
! #else
! 	{ 12,		WTAP_ENCAP_RAW_IP },
! #endif
! 
! 	/*
! 	 * 13 is DLT_SLIP_BSDOS on FreeBSD and NetBSD, but those OSes
! 	 * don't actually generate it.  I infer that BSD/OS translates
! 	 * DLT_SLIP from the kernel BPF code to DLT_SLIP_BSDOS in
! 	 * libpcap, as the BSD/OS link-layer header is different;
! 	 * however, in BSD/OS, DLT_SLIP_BSDOS is 15.
! 	 *
! 	 * From this, I infer that there's no point in handling 13
! 	 * as DLT_SLIP_BSDOS.
! 	 *
! 	 * 13 is DLT_ATM_RFC1483 on BSD/OS.
! 	 *
! 	 * 13 is DLT_ENC in OpenBSD, which is, I suspect, some kind
! 	 * of decrypted IPSEC traffic.
! 	 */
! #if defined(DLT_ATM_RFC1483) && (DLT_ATM_RFC1483 == 13)
! 	{ 13,		WTAP_ENCAP_ATM_RFC1483 },
! #elif defined(DLT_ENC) && (DLT_ENC == 13)
! 	/* Put entry for DLT_ENC here */
! #endif
! 
! 	/*
! 	 * 14 is DLT_PPP_BSDOS on FreeBSD and NetBSD, but those OSes
! 	 * don't actually generate it.  I infer that BSD/OS translates
! 	 * DLT_PPP from the kernel BPF code to DLT_PPP_BSDOS in
! 	 * libpcap, as the BSD/OS link-layer header is different;
! 	 * however, in BSD/OS, DLT_PPP_BSDOS is 16.
! 	 *
! 	 * From this, I infer that there's no point in handling 14
! 	 * as DLT_PPP_BSDOS.
! 	 *
! 	 * 14 is DLT_RAW on BSD/OS and OpenBSD.
! 	 */
! 	{ 14,		WTAP_ENCAP_RAW_IP },
! 
! 	/*
! 	 * 15 is:
! 	 *
! 	 *	DLT_SLIP_BSDOS on BSD/OS;
! 	 *
! 	 *	DLT_HIPPI on NetBSD;
! 	 *
! 	 *	DLT_LANE8023 with Alexey Kuznetzov's patches for
! 	 *	Linux libpcap;
! 	 *
! 	 *	DLT_I4L_RAWIP with the ISDN4Linux patches for libpcap
! 	 *	(and on SuSE 6.3);
! 	 *
! 	 * but we don't currently handle any of those.
! 	 */
! 
! 	/*
! 	 * 16 is:
! 	 *
! 	 *	DLT_PPP_BSDOS on BSD/OS;
! 	 *
! 	 *	DLT_HDLC on NetBSD;
! 	 *
! 	 *	DLT_CIP with Alexey Kuznetzov's patches for
! 	 *	Linux libpcap - this is WTAP_ENCAP_LINUX_ATM_CLIP;
! 	 *
! 	 *	DLT_I4L_IP with the ISDN4Linux patches for libpcap
! 	 *	(and on SuSE 6.3).
! 	 */
! #if defined(DLT_CIP) && (DLT_CIP == 16)
! 	{ 16,		WTAP_ENCAP_LINUX_ATM_CLIP },
! #endif
! 
! 	/*
! 	 * 17 is DLT_LANE8023 in SuSE 6.3 libpcap; we don't currently
! 	 * handle it.
! 	 */
! 
! 	/*
! 	 * 18 is DLT_CIP in SuSE 6.3 libpcap; if it's the same as the
! 	 * DLT_CIP of 16 that the Alexey Kuznetzov patches for
! 	 * libpcap/tcpdump define, it's WTAP_ENCAP_LINUX_ATM_CLIP.
! 	 * I've not found any libpcap that uses it for any other purpose -
! 	 * hopefully nobody will do so in the future.
! 	 */
! 	{ 18,		WTAP_ENCAP_LINUX_ATM_CLIP },
! 
! 	/*
! 	 * 19 is DLT_ATM_CLIP in the libpcap/tcpdump patches in the
! 	 * recent versions I've seen of the Linux ATM distribution;
! 	 * I've not yet found any libpcap that uses it for any other
! 	 * purpose - hopefully nobody will do so in the future.
! 	 */
! 	{ 19,		WTAP_ENCAP_LINUX_ATM_CLIP },
! 
! 	/*
! 	 * These are the values that libpcap 0.5 uses, in an attempt
! 	 * to work around the confusion decried above, and that Wiretap
! 	 * and Ethereal currently support.
! 	 */
! 	{ 100,		WTAP_ENCAP_ATM_RFC1483 },
! 	{ 101,		WTAP_ENCAP_RAW_IP }
  };
! #define NUM_PCAP_ENCAPS (sizeof pcap_to_wtap_map / sizeof pcap_to_wtap_map[0])
  
  int libpcap_open(wtap *wth, int *err)
  {
***************
*** 121,126 ****
--- 248,254 ----
  	struct pcap_hdr hdr;
  	gboolean byte_swapped;
  	gboolean modified;
+ 	int file_encap;
  	struct pcaprec_modified_hdr first_rec_hdr;
  	struct pcaprec_modified_hdr second_rec_hdr;
  	int hdr_len;
***************
*** 200,207 ****
  		*err = WTAP_ERR_UNSUPPORTED;
  		return -1;
  	}
! 	if (hdr.network >= NUM_PCAP_ENCAPS
! 	    || pcap_encap[hdr.network] == WTAP_ENCAP_UNKNOWN) {
  		g_message("pcap: network type %u unknown or unsupported",
  		    hdr.network);
  		*err = WTAP_ERR_UNSUPPORTED_ENCAP;
--- 328,335 ----
  		*err = WTAP_ERR_UNSUPPORTED;
  		return -1;
  	}
! 	file_encap = wtap_pcap_encap_to_wtap_encap(hdr.network);
! 	if (file_encap == WTAP_ENCAP_UNKNOWN) {
  		g_message("pcap: network type %u unknown or unsupported",
  		    hdr.network);
  		*err = WTAP_ERR_UNSUPPORTED_ENCAP;
***************
*** 217,223 ****
  	wth->subtype_read = libpcap_read;
  	wth->subtype_seek_read = wtap_def_seek_read;
  	wth->subtype_close = libpcap_close;
! 	wth->file_encap = pcap_encap[hdr.network];
  	wth->snapshot_length = hdr.snaplen;
  
  	/*
--- 345,351 ----
  	wth->subtype_read = libpcap_read;
  	wth->subtype_seek_read = wtap_def_seek_read;
  	wth->subtype_close = libpcap_close;
! 	wth->file_encap = file_encap;
  	wth->snapshot_length = hdr.snaplen;
  
  	/*
***************
*** 442,469 ****
  
  int wtap_pcap_encap_to_wtap_encap(int encap)
  {
! 	if (encap < 0 || encap >= NUM_PCAP_ENCAPS)
! 		return WTAP_ENCAP_UNKNOWN;
! 	return pcap_encap[encap];
  }
  
! static const int wtap_encap[] = {
! 	-1,		/* WTAP_ENCAP_UNKNOWN -> unsupported */
! 	1,		/* WTAP_ENCAP_ETHERNET -> DLT_EN10MB */
! 	6,		/* WTAP_ENCAP_TR -> DLT_IEEE802 */
! 	8,		/* WTAP_ENCAP_SLIP -> DLT_SLIP */
! 	9,		/* WTAP_ENCAP_PPP -> DLT_PPP */
! 	10,		/* WTAP_ENCAP_FDDI -> DLT_FDDI */
! 	10,		/* WTAP_ENCAP_FDDI_BITSWAPPED -> DLT_FDDI */
! 	12,		/* WTAP_ENCAP_RAW_IP -> DLT_RAW */
! 	7,		/* WTAP_ENCAP_ARCNET -> DLT_ARCNET */
! 	11,		/* WTAP_ENCAP_ATM_RFC1483 -> DLT_ATM_RFC1483 */
! 	19,		/* WTAP_ENCAP_LINUX_ATM_CLIP */
! 	-1,		/* WTAP_ENCAP_LAPB -> unsupported*/
! 	-1,		/* WTAP_ENCAP_ATM_SNIFFER -> unsupported */
! 	0		/* WTAP_ENCAP_NULL -> DLT_NULL */
! };
! #define NUM_WTAP_ENCAPS (sizeof wtap_encap / sizeof wtap_encap[0])
  
  /* Returns 0 if we could write the specified encapsulation type,
     an error indication otherwise. */
--- 570,603 ----
  
  int wtap_pcap_encap_to_wtap_encap(int encap)
  {
! 	int i;
! 
! 	for (i = 0; i < NUM_PCAP_ENCAPS; i++) {
! 		if (pcap_to_wtap_map[i].dlt_value == encap)
! 			return pcap_to_wtap_map[i].wtap_encap_value;
! 	}
! 	return WTAP_ENCAP_UNKNOWN;
  }
  
! static int wtap_wtap_encap_to_pcap_encap(int encap)
! {
! 	int i;
! 
! 	/*
! 	 * Special-case WTAP_ENCAP_FDDI and WTAP_ENCAP_FDDI_BITSWAPPED;
! 	 * both of them get mapped to DLT_FDDI (even though that may
! 	 * mean that the bit order in the FDDI MAC addresses is wrong;
! 	 * so it goes - libpcap format doesn't record the byte order,
! 	 * so that's not fixable).
! 	 */
! 	if (encap == WTAP_ENCAP_FDDI || encap == WTAP_ENCAP_FDDI_BITSWAPPED)
! 		return 10;	/* that's DLT_FDDI */
! 	for (i = 0; i < NUM_PCAP_ENCAPS; i++) {
! 		if (pcap_to_wtap_map[i].wtap_encap_value == encap)
! 			return pcap_to_wtap_map[i].dlt_value;
! 	}
! 	return -1;
! }
  
  /* Returns 0 if we could write the specified encapsulation type,
     an error indication otherwise. */
***************
*** 473,479 ****
  	if (encap == WTAP_ENCAP_PER_PACKET)
  		return WTAP_ERR_ENCAP_PER_PACKET_UNSUPPORTED;
  
! 	if (encap < 0 || encap >= NUM_WTAP_ENCAPS || wtap_encap[encap] == -1)
  		return WTAP_ERR_UNSUPPORTED_ENCAP;
  
  	return 0;
--- 607,613 ----
  	if (encap == WTAP_ENCAP_PER_PACKET)
  		return WTAP_ERR_ENCAP_PER_PACKET_UNSUPPORTED;
  
! 	if (wtap_wtap_encap_to_pcap_encap(encap) == -1)
  		return WTAP_ERR_UNSUPPORTED_ENCAP;
  
  	return 0;
***************
*** 526,532 ****
  	file_hdr.thiszone = 0;	/* XXX - current offset? */
  	file_hdr.sigfigs = 0;	/* unknown, but also apparently unused */
  	file_hdr.snaplen = wdh->snaplen;
! 	file_hdr.network = wtap_encap[wdh->encap];
  	nwritten = fwrite(&file_hdr, 1, sizeof file_hdr, wdh->fh);
  	if (nwritten != sizeof file_hdr) {
  		if (nwritten < 0)
--- 660,666 ----
  	file_hdr.thiszone = 0;	/* XXX - current offset? */
  	file_hdr.sigfigs = 0;	/* unknown, but also apparently unused */
  	file_hdr.snaplen = wdh->snaplen;
! 	file_hdr.network = wtap_wtap_encap_to_pcap_encap(wdh->encap);
  	nwritten = fwrite(&file_hdr, 1, sizeof file_hdr, wdh->fh);
  	if (nwritten != sizeof file_hdr) {
  		if (nwritten < 0)