Date: Mon, 17 Sep 2001 10:30:56 -0700 (PDT) From: Brad Knotwell <knotwell@ix.netcom.com> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/30634: kevent.data value incorrect for UDP sockets Message-ID: <200109171730.f8HHUub00713@freefall.freebsd.org>
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>Number: 30634
>Category: kern
>Synopsis: kevent.data value incorrect for UDP sockets
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Mon Sep 17 10:40:03 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator: Brad Knotwell
>Release: 4.2
>Organization:
home
>Environment:
FreeBSD freebsd 4.2-RELEASE FreeBSD 4.2-RELEASE #3: Thu Jul 19
root@freebsd:/usr/src/sys/compile/ALPHA-SVR i386
>Description:
When kevent returns a read event for a UDP socket, the data field (AKA the number of bytes to be read) is 16 bytes too long.
NOTE: the problem exists in 4.3 release as well.
>How-To-Repeat:
1) Compile up the following discard server
2) Run nc -u 127.0.0.1 6060
3) Send data to netcat and watch the server's output
It should be consistently off by sixteen bytes. NOTE: this may be a documentation bug and "the number of bytes in the socket buffer" needs to be explained further.
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/event.h>
/* loopback discardserver on port 6060 */
int main(void)
{
int queue,sock;
struct sockaddr_in saddr;
struct kevent evt;
memset(&saddr,0,sizeof(struct sockaddr_in));
saddr.sin_family = AF_INET;
saddr.sin_port = htons(6060);
saddr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
memset(&evt,0,sizeof(struct kevent));
evt.filter = EVFILT_READ;
evt.flags = EV_ADD;
if(((queue = kqueue()) == -1) ||
((evt.ident = (sock = socket(AF_INET,SOCK_DGRAM,0))) == -1) ||
(bind(sock,(struct sockaddr *)&saddr,sizeof saddr)) ||
(kevent(queue,&evt,1,NULL,0,NULL)))
return(fprintf(stderr,"bad setup\n"),EXIT_FAILURE);
while(1){
char *buf;
if((kevent(queue,NULL,0,&evt,1,NULL) == -1) ||
(!evt.data))
break;
if((buf = malloc(evt.data)) == NULL) continue;
recv(sock,buf,evt.data,0);
printf("size to read(%d) : data : %s\n",evt.data,buf);
free(buf);
}
return(EXIT_SUCCESS);
}
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:
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