Hamachi hardware checksum support

[pmonta@halibut.imedia.com]

> Were those the optimal parameters?  Did you try 64K or 128K nbuf and buflen ...

A 130000-byte rcvbuf on the receive machine helped quite
a bit ("-b 65000") if I remember right.  I'll try to give it
a spin tonight; thanks very much for the code.

Small tweak below for viewing the buffer sizes as they
actually end up; defaults and maxima can be tuned via
/proc/sys/net/core/{wmem,rmem}*.

Cheers,
Peter Monta   pmonta@imedia.com
Imedia Corp.

--- ttcp.c~     Mon Jan 18 22:38:56 1999
+++ ttcp.c      Sun Feb 14 00:02:15 1999
@@ -309,6 +309,11 @@
        }
 #endif
 
+       { int sndbuf=0,rcvbuf=0,t;
+         getsockopt(fd, SOL_SOCKET, SO_SNDBUF, &sndbuf, &t);
+         getsockopt(fd, SOL_SOCKET, SO_RCVBUF, &rcvbuf, &t);
+         fprintf(stderr,"sndbuf, rcvbuf: %d %d\n",sndbuf,rcvbuf); }
+
        if (!udp)  {
            signal(SIGPIPE, sigpipe);
            if (trans) {
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