On Mar 12, 2004, at 2:03 AM, Mark Pizzolato wrote:
I've been working on a system simulator (simh http://simh.trailing-edge.com)
which provides ethernet device emulation for the systems which originally
had ethernet devices (i.e. vax, pdp11 and pdp10).
The ethernet support for this package was originally implemented on Windows
with Winpcap, and then ported back to other platforms leveraging the generic
libpcap capabilities. The only lacking piece here, from an API poinit of
view, has been pcap_sendpacket. Just to get by, we've had platform specific
network code in the layer which uses libpcap to provide a pcap_sendpacket
for the non Windows platforms. This only solves part of the problem since
several platforms use pcap-bpf.c or pcap-pf.c or pcap-snit.c which open the
network device O_RDONLY. To get useful functionality on these platforms,
we've needed to hack pcap-bpf.c, or pcap-pf.c or pcap-snit.c and change
O_RDONLY to O_RDWR. If would seem that the right thing to do is to
generically include pcap_sendpacket and the related open requirements in the
base pcap library.
Well, the right thing to do is not necessarily to change O_RDONLY to O_RDWR, as that would mean you can't give people "capture but not send" privileges on BPF platforms by giving them read but not write access to the BPF devices.
The best thing to do probably is to add a new API for opening captures that lets you specify whether you're opening for capturing, sending, or both; the new API can also fix a number of other problems (setting the internal capture buffer size - which, on BPF devices, must be done before the BPF device is bound to an interface; allowing things such as monitor mode to be specified at open time; supporting remote capture, as per WinPcap's "pcap_open_ex()"; etc.).
In pcap.h, I've messed with PCA_MINOR_VERSION in an attempt to have the
code which uses pcap.h to have a compile time means of determinig if
pcap_sendpacket is available:
#if (_WIN32) || (PCAP_MAJOR_VERSION > 2) || ((PCAP_MAJOR_VERSION == 2) &&
(PCAP_MINOR_VERSION > 4))
#define HAS_PCAP_SENDPACKET 1
#endif
Is there a better way to do this at compile time?
autoconf.
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