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From: Gerold Jury <gjury@hal.grips.com>
To: root@chaos.analogic.com
Subject: Re: want opinions on possible glitch in 2.4 network error reporting
Date: Thu, 7 Feb 2002 17:33:31 +0100
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This is off topic but close.
UDP packets are not dropped when the UDP socket is shutdown(socket,0); for 
receive at least on 2.4.17.
attached is a small proof.
Anyone with a hint or a fix ?

Thanks
Gerold


On Thursday 07 February 2002 14:44, Richard B. Johnson wrote:
>
>        ENOBUFS
>               The output queue for a network interface was  full.
>               This  generally  indicates  that  the interface has
>               stopped sending, but may  be  caused  by  transient
>               congestion.   (This  cannot occur in Linux, packets
>               are just silently dropped when a device queue over?
>               flows.)
>
>
> Linux Man Page              July 1999                           1
>

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  name="udpshutdown.c"
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#include <stdio.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

char hello[] = "hello socket";
char buf[2048];

int main( int argc, char *argv[] )
{
  int iFd, ret;
  socklen_t fromlen;
  short port = 15678;
  struct sockaddr_in addr, from;

  if((iFd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
    perror("create socket");
    exit( 0 );
  }
  addr.sin_family = AF_INET;
  addr.sin_port = htons( port );
  addr.sin_addr.s_addr = htonl( INADDR_LOOPBACK );
  if (bind( iFd, (struct sockaddr *)&addr, sizeof( addr ) ) < 0) {
    fprintf(stderr,"bind to %d failed %s\n",port,strerror(errno));
    exit( 0 );
  }
  shutdown( iFd, 0 ); // shutdown receive
  // addr.sin_addr.s_addr = htonl( INADDR_LOOPBACK );
  if( sendto( iFd, hello, sizeof( hello ), 0, (struct sockaddr *)&addr, sizeof( addr ) ) < 0 ) {
    perror("sendto");
    exit( 0 );
  }
  ret = recvfrom( iFd,  buf, sizeof( buf ), 0, (struct sockaddr *)&from, &fromlen );
  if( ret < 0 ) {
    perror("recvfrom");
    exit( 0 );
  }
  printf( "received %d bytes [%s]\n", ret, buf );

  shutdown( iFd, 1 ); // shutdown send
  if( sendto( iFd, hello, sizeof( hello ), 0, (struct sockaddr *)&addr, sizeof( addr ) ) < 0 ) {
    perror("sendto");
    exit( 0 );
  }
  return 0;
}

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