Reply-To: "Jean-Paul ROUBELAT" <jpr@f6fbb.org>
From: "Jean-Paul ROUBELAT" <jpr@f6fbb.org>
To: "Craig Small" <csmall@scooter.eye-net.com.au>
References: <E10zTcx-0000ih-00@scooter.eye-net.com.au>
Subject: rspfd again
Date: Mon, 24 Jan 2000 22:19:46 +0100
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Hi Craig,

I worked a bit more on rspfd 1.0. It now almost work.

Some comments on the checksum computation routine which gave me the problems
:

Hi Craig,

I worked a little bit more on rspf 1.0 and found some possible problems
in the checksum routine. It explains why no packet were accepted here.

---

unsigned short rspf_check(unsigned char *rh, int len,
  unsigned long saddr, unsigned long daddr)
{     
 unsigned long sum;
 unsigned short *sp;
 int i;
   
 sp = (unsigned short*)rh;
 /* Zero the checksum */
 sum = 0;

 /* Source address */
 sum += (saddr & 0xffff);
 sum += (saddr < 16 ); <<- should be sum += (saddr >> 16 )  ?

 sum += (daddr & 0xffff);
 sum += (daddr < 16);  <<- IDEM
 sum += IPPROTO_UDP;

 for(i=0;i<len;i++)    <<- must be len/2 (short pointer, len in chars)
 {
  sum += sp[i];
 }

 sum = (sum >> 16) + (sum & 0xffff);
 sum += (sum >> 16);   <<- just done before ?

 return (unsigned short)(~sum & 0xffff);
}


73,
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