ARPHRD_IEEE802, as the hardware type for Token Ring interfaces. Map
both of them to DLT_IEEE802 (as that has become the DLT_ type for Token
Ring, the fact that it just says "802", not "802_5" or whatever,
nonwithstanding), and, if ARPHRD_IEEE802_TR isn't defined, define it
with the value it has in 2.4 (so that the resulting libpcap will work on
a 2.4 system regardless of whether the system on which it was built
defined ARPHRD_IEEE802_TR).
filter, always attach a copy, as "pcap-linux.c" does; that way, after a
program uses "pcap_setfilter()", it can safely use "pcap_freecode()" to
free up the BPF instructions allocated by "pcap_compile()". Also,
always free it up when the "pcap_t" is closed.
Get rid of the "pcap_t *" argument to "pcap_freecode()", as it's not
necessary.
Document "pcap_freecode()", for the benefit of programs that might
repeatedly compile filter programs and attach them, so that they can
free them up after attaching them and avoid leaking memory for them.
interface index of the interface for the packet is the interface index
of the loopback interface and, if it is, check if the packet is an
outgoing packet; if so, ignore it, as we'll also be seeing that packet
as a received packet.
If we don't handle the arphrd type of an interface, and fall back on
cooked mode, report the arphrd type, so we know what type we should
consider supporting (if that type can't be supported well, e.g. if you
don't get any link-layer header, as happens with PPP, we'd be silent).
filter.
It appears that "recvfrom()", in 2.2 and later kernels, doesn't check
whether the starting buffer address plus the byte count goes into an
unmapped region of the address space - it (or code it calls) presumably
only checks the locations into which it's actually copying data - so
there doesn't appear to be, on systems with 2.2 and later kernels, any
need to ensure that the buffer size is at least large as the snapshot
length. We therefore only do so if we're using the old
PF_INET/SOCK_PACKET mechanism; if we're using PF_PACKET, we're on a
2.2 or later kernel, so we don't do it there.
"HAVE_NETPACKET_PACKET_H" isn't defined, as we won't define them if it's
not defined.
If the packet buffer size, as computed from the MTU of the interface, is
less than the user's requested snapshot length, set it to the user's
requested snapshot length; otherwise, the "recvfrom()" call will fail,
as the length specified in the call is the user's requested snapshot
length, and the kernel checks whether the buffer is big enough for that
much data and rejects the "recvfrom()" call if it's not.
application won't build with any other version of libpcap, which means
that a lot of applications won't use them. In addition,
"pcap_linktype()" needs to return DLT_ values, so that platforms that
build libpcap as a shared library won't break binary compatibility if
they update to this version of libpcap.
Instead, we map from DLT_ values to LINKTYPE_ values when writing
savefiles, and map from LINKTYPE_ values to DLT_ values when reading
savefiles, so that savefiles don't have platform-dependent DLT_ values
in the header as the link type, they have platform-independent LINKTYPE_
values.
This means we don't need to make DLT_ATM_RFC1483, DLT_RAW, etc. have
platform-independent values starting at 100 - only the values in the
savefile header need to be like that.
For those PCAP_ENCAP_ codes corresponding to DLT_ codes that are
(believed to be) the same in all BSDs, the PCAP_ENCAP_ codes have the
same values as the corresponding DLT_ codes.
For those PCAP_ENCAP_ codes corresponding to DLT_ codes that were added
in libpcap 0.5 as "non-kernel" DLT_ codes, or had their values changed
in libpcap 0.5 in order to cope with the fact that those DLT_ codes
have different values in different systems, the PCAP_ENCAP_ codes have
the same values as the corresponding DLT_ codes.
We add some additional PCAP_ENCAP_ codes to handle IEEE 802.11 (which
currently has its link-layer information turned into an Ethernet header
by at least some of the BSDs, but John Hawkinson at MIT wants to add a
DLT_ value for 802.11 and pass up the full link-layer header) and the
Classical IP encapsulation for ATM on Linux (which isn't always the same
as DLT_ATM_RFC1483, from what I can tell, alas).
"pcap-bpf.c" maps DLT_ codes to PCAP_ENCAP_ codes, so as not to supply
to libpcap's callers any DLT_ codes other than the ones that have the
same values on all platforms; it supplies PCAP_ENCAP_ codes for all
others.
In libpcap's "bpf/net/bpf.h", we define the DLT_ values that aren't the
same on all platforms with the new values starting at 100 (to keep them
out of the way of the values various BSDs might assign to them), as we
did in 0.5, but do so only if they're not already defined; platforms
with <net/bpf.h> headers that come with the kernel (e.g., the BSDs)
should define them with the values that they have always had on that
platform, *not* with the values we used in 0.5.
(Code using this version of libpcap should check for the new PCAP_ENCAP_
codes; those are given the values that the corresponding DLT_ values had
in 0.5, so code that checks for them will handle 0.5 libpcap files
correctly even if the platform defines DLT_RAW, say, as something other
than 101. If that code also checks for DLT_RAW - which means it can't
just use a switch statement, as DLT_RAW might be defined as 101 if the
platform doesn't itself define DLT_RAW with some other value - then it
will also handle old DLT_RAW captures, as long as they were made on the
same platform or on another platform that used the same value for
DLT_RAW. It can't handle captures from a platform that uses that value
for another DLT_ code, but that's always been the case, and isn't easily
fixable.)
The intent here is to decouple the values that are returned by
"pcap_datalink()" and put into the header of tcpdump/libpcap save files
from the DLT_ values returned by BIOCGDLT in BSD kernels, allowing the
BSDs to assign values to DLT_ codes, in their kernels, as they choose,
without creating more incompatibilities between tcpdump/libpcap save
files from different platforms.
guy