Re: Libpcap reentrancy and PF_RING patch

["Paolo Abeni" <paolo.abeni () telecomitalia it>]

hello,

On Sun, 2007-12-30 at 12:09 +0100, Luca Deri wrote:
> please find enclosed a patch (against the code that's in CVS) that  
> adds reentrancy in pcap.

There is an issue with the linux/usb code:

===================================================================
RCS file: /tcpdump/master/libpcap/pcap-usb-linux.c,v
retrieving revision 1.20
diff -r1.20 pcap-usb-linux.c
652c652
< usb_read_linux_mmap(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user)
---
> usb_read_linux_mmap(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user, u_char *buf, u_short 
> bufsize)
696c696
<                       hdr = (pcap_usb_header*) &handle->buffer[vec[i]];
---
>                       hdr = (pcap_usb_header*) &buf[vec[i]];


Here handle->buffer refers to a memory mapped kernel buffer, which holds
the USB Request Blocks and related meta-data. To make the patch work is
necessary to perform a memcpy from the kernel buffer to the user
provided one, but this solution will remove the performance gain of the
memory mapped access.

ciao,

Paolo
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