Re: [PACTH] enable memory mapped access to ethernet

[Guy Harris <guy () alum mit edu>]

Paolo Abeni wrote:

> Any comments on this matter or on the patch are very welcome !

If, in pcap_open_live(), live_open_mmap() succeeds, 
handle->selectable_fd doesn't get set.

This will break, among other programs, the current version of Wireshark, 
and the upcoming version of Wireshark.  (A similar problem in 
pcap-usb-linux.c appear to have already broken USB capture; see recent 
mails in the wireshark-dev mailing list.)

If live_open_mmap() succeeded, can a select() or poll() on the mapped FD 
be done to wait for packets to arrive?  If so, you need to set 
handle->selectable_fd to handle->fd before returning.  If *not*, you 
need to set it to -1 before returning, to indicate that you can't use 
select() or poll() to wait for packets to arrive.

(While we're on that topic, can select() or poll() be used for USB 
capture?  I've checked in changes to pcap-usb-linux.c that assume it 
can; if not, it needs to set handle->selectable_fd to -1 in the 
memory-mapped case.)
-
This is the tcpdump-workers list.
Visit https://cod.sandelman.ca/ to unsubscribe.