Ivan Pulleyn <ivan@sixfold.com> writes:
> What was the sysctl value for net.ipv4.tcp_syn_max_backlog set to
> while running this test? That's the value you are testing, not the
> listen() queue size.
The value of net.ipv4.tcp_syn_max_backlog does not matter. Even if I
set it to zero, I can create several hundred of connections without
accept()'ing any. And netstat show them all in the CONNECTED state.
That looks bad to me.
Phil.
> On 27 Nov 2002, Philippe Troin wrote:
>
> > [Andi, I've CC'ed you since you're listed as the author of the `new
> > listen' code in net/ipv4/tcp_ipv4.c]
> >
> > Seen on linux 2.4.20rc2.
> >
> > This program is always able to establish new connections to itself:
> > the accept queue never fills up and connections always succeed
> > (although they take quite some time after the first four):
> >
> > #include <stdio.h>
> > #include <sys/types.h>
> > #include <sys/socket.h>
> > #include <netinet/in.h>
> >
> > int main(void)
> > {
> > int fd;
> > struct sockaddr_in sin;
> > socklen_t sinlen;
> >
> > if ((fd = socket(PF_INET, SOCK_STREAM, 0)) == -1)
> > perror("socket"), exit(1);
> >
> > sin.sin_family = AF_INET;
> > sin.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
> > sin.sin_port = htons(0);
> > if (bind(fd, (struct sockaddr*)&sin, sizeof(sin)) == -1)
> > perror("bind"), exit(1);
> > if (listen(fd, 1) == -1)
> > perror("listen"), exit(1);
> >
> > sinlen = sizeof(sin);
> > getsockname(fd, (struct sockaddr*)&sin, &sinlen);
> >
> > while (1)
> > {
> > int fdc;
> >
> > if ((fdc = socket(PF_INET, SOCK_STREAM, 0)) == -1)
> > perror("socket"), exit(1);
> > printf("%c", connect(fdc, (struct sockaddr*)&sin, sinlen) == -1
> > ? 'F' : '.');
> > fflush(stdout);
> > }
> >
> > exit(0);
> > }
> >
> > I've tried enabling and disabling tcp_syncookies, without any effect.
> >
> > The same program starts returning errors after two successful connects
> > on Solaris and one on HP-UX. Linux keeps returning new connections...
> >
> > Phil.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Sat Dec 07 2002 - 22:00:15 EST