Add sample strace output to illustrate the timeout problem.

svn path=/trunk/; revision=1395

README.linux

@@ -1,4 +1,4 @@
-$Id: README.linux,v 1.1 1999/08/31 06:09:25 gram Exp $
+$Id: README.linux,v 1.2 1999/12/29 21:33:06 gerald Exp $
 
 The standard libpcap compiled for Linux has a timeout problem.
 If you use Ethereal with this libpcap on a not-so-busy network, at
@@ -14,3 +14,20 @@ Libpcap can be obtained from ftp://ftp.ee.lbl.gov
 
 You can download the Linux patch at http://ethereal.zing.org/~gerald/
 
+Modified RedHat 6.0 and 6.1 libpcap RPMs are available at
+ftp://ethereal.zing.org/pub/ethereal/rpms
+
+
+To illustrate the problem, below is the output of strace on Ethereal
+using a stock version of libpcap, followed by a "fixed" version.
+Note that in the "fixed" version select() is called before recvfrom().
+The use of select() allows the packet capture to time out if there is
+no incoming data.
+
+30677 08:30:30 poll([{fd=4, events=POLLIN}, {fd=5, events=POLLIN}], 2, 0) = 0
+30677 08:30:30 recvfrom(8, "\0\20{\357;\333\10\0 }\200\302\10\0E\0\0(\22\23@\0\377"..., 65535, 0x20, {sa_family=17, sa_data="\10\0\0\0\0\2\0\1\3\6\10\0 }"}, [20]) = 60
+
+30914 09:05:48 poll([{fd=4, events=POLLIN}, {fd=5, events=POLLIN}], 2, 0) = 0
+30914 09:05:48 select(9, [8], NULL, NULL, {0, 250000}) = 1 (in [8], left {0, 250000})
+30914 09:05:48 recvfrom(8, "\10\0 }\200\302\0\20{\357;\333\10\0E\10\5\334-\323@\0\363"..., 65535, 0x20, {sa_family=17, sa_data="\10\0\0\0\0\2\0\1\3\6\0\20{\357"}, [20]) = 1514
+