in the test program below the getsockname result on a TCP socket changes
across a write which produces EPIPE... here's a fragment of the strace:
getsockname(3, {sa_family=AF_INET, sin_port=htons(37636),
sin_addr=inet_addr("127.0.0.1")}, [17863593746633850896]) = 0
...
write(3, "hi!\n", 4) = 4
write(3, "hi!\n", 4) = -1 EPIPE (Broken pipe)
--- SIGPIPE (Broken pipe) @ 0 (0) ---
getsockname(3, {sa_family=AF_INET, sin_port=htons(59882),
sin_addr=inet_addr("127.0.0.1")}, [16927060683038654480]) = 0
why does the port# change? this is on 2.6.19.1.
(fwiw this is one of two reasons i've found for libnss-ldap to leak
sockets... causing nscd to crash.)
-dean
reproduce like:
make test-sockname-change
nc -l -p 9999 -c "exit 0" &
strace ./test-sockname-change 127.0.0.1 9999
--- snip ---
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <stdlib.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/uio.h>
#include <errno.h>
#include <signal.h>
#include <fcntl.h>
#ifndef INADDR_NONE
#define INADDR_NONE (-1ul)
#endif
int main(int argc, char **argv)
{
struct sockaddr_in server_addr;
struct sockaddr_in before, after;
socklen_t slen;
int s;
struct iovec vector[3];
char buf[100];
int i;
const int just_say_no = 1;
if (argc != 3) {
usage:
fprintf(stderr, "usage: test-sigpipe a.b.c.d port#\n");
exit(1);
}
server_addr.sin_family = AF_INET;
server_addr.sin_addr.s_addr = inet_addr(argv[1]);
if (server_addr.sin_addr.s_addr == INADDR_NONE) {
fprintf(stderr, "bogus address\n");
goto usage;
}
server_addr.sin_port = htons(atoi(argv[2]));
s = socket(AF_INET, SOCK_STREAM, 0);
if (s < 0) {
perror("socket");
exit(1);
}
if (connect(s, (struct sockaddr *)&server_addr, sizeof(server_addr)) != 0) {
perror("connect");
exit(1);
}
if (setsockopt(s, IPPROTO_TCP, TCP_NODELAY, (char*)&just_say_no,
sizeof(just_say_no)) != 0) {
perror( "TCP_NODELAY" );
exit(1);
}
fcntl(s, F_SETFL, fcntl(s, F_GETFL) | O_NONBLOCK);
slen = sizeof(before);
if (getsockname(s, (struct sockaddr *)&before, &slen)) {
perror("getsockname before");
}
signal(SIGPIPE, SIG_IGN);
sleep(1);
do {
i = write(s, "hi!\n", 4);
} while (i >= 0);
if (errno != EPIPE) {
fprintf(stderr, "was expecting EPIPE from write\n");
exit(1);
}
slen = sizeof(after);
if (getsockname(s, (struct sockaddr *)&after, &slen)) {
perror("getsockname after");
}
printf("before = %d, after = %d\n", ntohs(before.sin_port),
ntohs(after.sin_port));
return 0;
}
-
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