About DLT_LANE8023 and lane_if_print()

[Guy Harris via tcpdump-workers <tcpdump-workers () lists tcpdump org>]

> --- Begin Message ---
>
>
> From: Guy Harris <gharris () sonic net>
>
> Date: Fri, 7 Aug 2020 15:41:29 -0700
>
> On Aug 4, 2020, at 1:28 PM, Francois-Xavier Le Bail <devel.fx.lebail () orange fr> wrote:
>
> > lane_if_print() in print-lane.c
> > (Added by 77b2a4405561467f66a3dfb0f8ce2b0eaa5ebaf9 in Sun Nov 21 1999 "print of ATM LanEmulation")
> > is called for DLT_LANE8023:
> >
> > print.c-56-#ifdef DLT_LANE8023
> > print.c:57:     { lane_if_print,        DLT_LANE8023 },
> > print.c-58-#endif
> > (Added by 777892a591065d32fb8744675574f9214398283a in Sun Nov 21 1999 "add lane and cip printing")
> >
> > But DLT_LANE8023 was never defined in libpcap nor tcpdump.
>
> A comment in pcap/dlt.h says:
>
> /*
> * 17 was used for DLT_PFLOG in OpenBSD; it no longer is.
> *
> * It was DLT_LANE8023 in SuSE 6.3, so we defined LINKTYPE_PFLOG
> * as 117 so that pflog captures would use a link-layer header type
> * value that didn't collide with any other values.  On all
> * platforms other than OpenBSD, we defined DLT_PFLOG as 117,
> * and we mapped between LINKTYPE_PFLOG and DLT_PFLOG.
> *
> * OpenBSD eventually switched to using 117 for DLT_PFLOG as well.
> *
> * Don't use 17 for anything else.
> */
>
> However, I downloaded ISO disk 6 from
>
>         https://archive.org/download/SuSE6.3-full
>
> mounted it (macOS diskimages-helper for the win!), copied libpcap-0.4a6.spm, turned it into a cpis file with rpm2cpio, 
> and extracted the contents; I can't see DLT_LANE8023 in either the source (which may be a vanilla version of libpcap 
> 0.4a6, often mistakenly thought to be the last libpcap from LBL - 0.4 non-alpha was) or in the SuSE patch, so either
>
>         1) there was no DLT_LANE8023 in SuSE 6.3;
>
>         2) there was, but it wasn't in libpcap;
>
>         3) there was, but it wasn't in *that* libpcap, it was in some *other* libpcap (but I couldn't find any other 
> libpcap);
>
>         4) that's not an image of SuSE 6.3.
>
> So I checked my mailbox, and found a message from 2000(!) to the ethereal-dev mailing list:
>
>         https://www.wireshark.org/lists/ethereal-users/200008/msg00159.html
>
> in which, among other things, I said:
>
> > So I downloaded an RPM from SuSE's Web site, and the "bpf.h" in it says:
> >
> >       /* Warning: not binary compatible with ANK libpcap !!! */
> >       #define DLT_LANE8023    17      /* LANE 802.3(Ethernet) */
> >       #define DLT_CIP         18      /* ATM Classical IP */
>
> and
>
> > And then, in Linuxland:
> >
> >       We have Alexey's patches - which may just have picked stuff up
> >       from elsewhere - which add
> >
> >               #define DLT_LANE8023    15      /* LANE 802.3(Ethernet) */
> >               #define DLT_CIP         16      /* ATM Classical IP */
> >
> >       We have the ISDN4Linux patches, which add
> >
> >               #define DLT_I4L_RAWIP   15      /* isdn4linux: rawip */
> >               #define DLT_I4L_IP      16      /* isdn4linux: ip */
> >
> >       And now we have SuSE's, which add the ISDN4Linux stuff, and then
> >       add the stuff from Alexey's patches *but with different
> >       numbers from the ones in his patches*.
>
> I'm not sure what RPM that was, but the idea was, presumably, that *if* you built tcpdump on a system that *did* define 
> DLT_LANE8023 in *its* libpcap, and used *its* libpcap, it could print packets that used DLT_LANE8023.
>
> ("Alexey"/"ANK" is Alexey Kuznetzov who, among other things, created the "turbopacket" patch to the Linux PF_PACKET 
> socket code; that eventually got into the mainline kernel - the "T" in "TPACKET_V[123]" stands, I think, for "turbo".)
>
> > What to do with this?
>
> As far as I know, neither DLT_LANE8023 nor DLT_CIP are still around in any Linux distribution, so nuking support for 
> that's OK with me.  I'm not seeing any support for either of them in Wireshark.
>
> Current OpenSuSe Leap 15.2 does not have DLT_LANE8023 or DLT_CIP.
>
> Is there any reason to keep the code to handle those DLT_ values around?
>
> --- End Message ---
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