Cross thread shutdown of connected UDP socket, unexpected recvfrom behavior
Hi LKML,
I have a C/pthreads program with two threads ("main" and "thread").
"thread" calls recvfrom on a connected UDP socket and blocks, waiting
for input. "main" then calls shutdown SHUT_RD on the socket. In
"thread", recvfrom returns, apparently successfully, returning a zero
length string, and setting src_addr to a bogus(?) address family,
port, and source address.
Is the above the correct behavior for recvfrom?
Here is output from my program. "main" sends "hello\0", then "" (the
empty string), then calls shutdown. "thread" receives "hello\0", "",
and then finally receives an empty string that was never sent!
thread recvfrom: Success
rv 6 addrlen 16 fam 2 port 8000 addr 17f
thread recvfrom: Success
rv 0 addrlen 16 fam 2 port 8000 addr 17f
mainshutdown: Success
rv 0
thread recvfrom: Success
rv 0 addrlen 16 fam 59060 port 44237 addr deaadef0
The source code (2k) for the porgram is attached. I'm running Ubuntu
13.04, kernel 3.8.0-19-generic #30-Ubuntu, on 32-bit i686.
For reference, this June 2000 LKML thread discusses calling close in a
similar situation.
http://www.gossamer-threads.com/lists/linux/kernel/144379
Please CC me if you have questions, otherwise I'll try to watch for
answers in the list archives.
Thanks!
-mpb
#include
#include
#include
#include
#include
struct sockaddr_in addr_0, addr_1, addr_2 ;
int fd0, fd1, rv0, rv1, addrlen;
charbuf_0[1024], buf_1[1024];
pthread_t thread;
void* thread_rv;
void* thread_main (void* arg) {
int i; for ( i=0; i<3; i++ ) {
addr_2.sin_family = 0;
addr_2.sin_port = 0;
addr_2.sin_addr.s_addr = 0;
addrlen = sizeof addr_2;
rv1 = recvfrom ( fd1, buf_0, sizeof buf_0, 0,
(struct sockaddr*) _2, );
int fam = addr_2.sin_family;
int port = addr_2.sin_port;
int addr = addr_2.sin_addr.s_addr;
printf ("\n");
perror ("thread recvfrom");
printf ( " rv %d addrlen %d fam %d port %d addr %x\n",
rv1, addrlen, fam, ntohs (port), addr );
;;; }
return NULL; }
void main_main () {
send ( fd0, "hello", 6, 0);
send ( fd0, "", 0, 0);
usleep (10);
rv0 = shutdown ( fd1, SHUT_RD );
printf ("\n");
perror ("mainshutdown");
printf (" %d\n", rv0)
;;; }
int main () {
addr_0.sin_family = AF_INET;
addr_0.sin_port = htons (8000);
inet_pton ( AF_INET, "127.0.0.1", _0.sin_addr );
addr_1.sin_family = AF_INET;
addr_1.sin_port = htons (8001);
inet_pton ( AF_INET, "127.0.0.1", _1.sin_addr );
fd0 = socket ( AF_INET, SOCK_DGRAM, 0 );
bind( fd0, (struct sockaddr*) _0, sizeof addr_0 );
connect ( fd0, (struct sockaddr*) _1, sizeof addr_1 );
fd1 = socket ( AF_INET, SOCK_DGRAM, 0 );
bind( fd1, (struct sockaddr*) _1, sizeof addr_1 );
connect ( fd1, (struct sockaddr*) _0, sizeof addr_0 );
pthread_create ( , NULL, thread_main, NULL );
main_main ();
pthread_join ( thread, _rv );
return 0; }
Cross thread shutdown of connected UDP socket, unexpected recvfrom behavior
Hi LKML,
I have a C/pthreads program with two threads (main and thread).
thread calls recvfrom on a connected UDP socket and blocks, waiting
for input. main then calls shutdown SHUT_RD on the socket. In
thread, recvfrom returns, apparently successfully, returning a zero
length string, and setting src_addr to a bogus(?) address family,
port, and source address.
Is the above the correct behavior for recvfrom?
Here is output from my program. main sends hello\0, then (the
empty string), then calls shutdown. thread receives hello\0, ,
and then finally receives an empty string that was never sent!
thread recvfrom: Success
rv 6 addrlen 16 fam 2 port 8000 addr 17f
thread recvfrom: Success
rv 0 addrlen 16 fam 2 port 8000 addr 17f
mainshutdown: Success
rv 0
thread recvfrom: Success
rv 0 addrlen 16 fam 59060 port 44237 addr deaadef0
The source code (2k) for the porgram is attached. I'm running Ubuntu
13.04, kernel 3.8.0-19-generic #30-Ubuntu, on 32-bit i686.
For reference, this June 2000 LKML thread discusses calling close in a
similar situation.
http://www.gossamer-threads.com/lists/linux/kernel/144379
Please CC me if you have questions, otherwise I'll try to watch for
answers in the list archives.
Thanks!
-mpb
#include netinet/in.h
#include pthread.h
#include stdio.h
#include sys/socket.h
#include sys/types.h
struct sockaddr_in addr_0, addr_1, addr_2 ;
int fd0, fd1, rv0, rv1, addrlen;
charbuf_0[1024], buf_1[1024];
pthread_t thread;
void* thread_rv;
void* thread_main (void* arg) {
int i; for ( i=0; i3; i++ ) {
addr_2.sin_family = 0;
addr_2.sin_port = 0;
addr_2.sin_addr.s_addr = 0;
addrlen = sizeof addr_2;
rv1 = recvfrom ( fd1, buf_0, sizeof buf_0, 0,
(struct sockaddr*) addr_2, addrlen );
int fam = addr_2.sin_family;
int port = addr_2.sin_port;
int addr = addr_2.sin_addr.s_addr;
printf (\n);
perror (thread recvfrom);
printf ( rv %d addrlen %d fam %d port %d addr %x\n,
rv1, addrlen, fam, ntohs (port), addr );
;;; }
return NULL; }
void main_main () {
send ( fd0, hello, 6, 0);
send ( fd0, , 0, 0);
usleep (10);
rv0 = shutdown ( fd1, SHUT_RD );
printf (\n);
perror (mainshutdown);
printf ( %d\n, rv0)
;;; }
int main () {
addr_0.sin_family = AF_INET;
addr_0.sin_port = htons (8000);
inet_pton ( AF_INET, 127.0.0.1, addr_0.sin_addr );
addr_1.sin_family = AF_INET;
addr_1.sin_port = htons (8001);
inet_pton ( AF_INET, 127.0.0.1, addr_1.sin_addr );
fd0 = socket ( AF_INET, SOCK_DGRAM, 0 );
bind( fd0, (struct sockaddr*) addr_0, sizeof addr_0 );
connect ( fd0, (struct sockaddr*) addr_1, sizeof addr_1 );
fd1 = socket ( AF_INET, SOCK_DGRAM, 0 );
bind( fd1, (struct sockaddr*) addr_1, sizeof addr_1 );
connect ( fd1, (struct sockaddr*) addr_0, sizeof addr_0 );
pthread_create ( thread, NULL, thread_main, NULL );
main_main ();
pthread_join ( thread, thread_rv );
return 0; }
