Re: Build fails on system with ancient version of libpcap installed

[David Fifield <david () bamsoftware com>]

On Mon, Jan 31, 2011 at 01:24:40PM +0000, Paul Howarth wrote:
> Trying to build nmap - with the bundled libpcap - fails on systems
> with ancient versions of libpcap (e.g. 0.7.2) installed:
>
> $  ./configure \
>       --with-liblua=included \
>       --with-libpcap=included \
>       --without-nping
> ...
> gcc -c -I/usr/kerberos/include   -I../../nbase -DHAVE_CONFIG_H
> -DNSOCK_VERSION=\"0.02\" -D_FORTIFY_SOURCE=2 -I../include
> -I../../libpcap -O2 -g -pipe -march=i386 -mcpu=i686 -Wall
> nsock_pcap.c -o nsock_pcap.o
> In file included from ../../libpcap/pcap.h:45,
>                  from nsock_pcap.h:7,
>                  from nsock_pcap.c:12:
> ../../libpcap/pcap/pcap.h:352: error: conflicting types for `bpf_filter'
> /usr/include/net/bpf.h:448: error: previous declaration of `bpf_filter'
> ../../libpcap/pcap/pcap.h:353: error: conflicting types for `bpf_validate'
> /usr/include/net/bpf.h:447: error: previous declaration of `bpf_validate'
>
> What's happening here is that nsock's configure script is checking
> for <net/bpf.h> and finding it on the system, despite the fact that
> we're using the bundled libpcap, which doesn't supply that obsolete
> header file. So the old system libpcap header files are included in
> addition to the much newer bundled libpcap header files and we get
> the conflict above.
>
> A simple workaround for me was to tell the configure script that we
> don't have <net/bpf.h>:
>
> $ export ac_cv_header_net_bpf_h=no
> $ ./configure ...
>
> Perhaps the configure script could be tweaked not to check for this
> header if the included libpcap is being used in future versions?

Thanks for good analysis. Since you've looked into this already, could
you suggest how to make this change (or provide a patch)? That spares
someone from having to simulate or install an old libpcap to test the
change.

David Fifield
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