After installing Redhat 6.0 on a production server, I
noticed a problem with syslogd.  syslogd was growing in
memory size proportional to the amount of data received.
This is a box that is doing lots and lots of syslogging from
lots of hosts.

Well after some investigation, and examining of the source
code, I have isolated the bug.  And I am including a sample
program that shows the bug.

It appears that if you call gethostbyaddr, and if the
address is not in /etc/hosts, the gethostbyaddr call leaks
memory.  If the address is in /etc/hosts (which is what we
did to solve the problem for now), it does not leak.  The
program below will call gethostbyaddr 100,000 times, and
then pause so you can take a look at the size of the
process.  Under 5.2 the process does not grow in size.
Under 6.0 the process grows rapidly.

test.c
----------------------------
#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
void main()
{
        unsigned long n = 0x24b445cf;
        int i;
        struct hostent *hp = 0, *ohp = 0;
        struct sockaddr_in f;
        struct sockaddr_in *f2 = &f;
        f.sin_addr.s_addr = 0xCF45B424;
        f.sin_family = AF_INET;
        for (i=0; i<100000; i++) {
                hp = gethostbyaddr((char *) &n, 4, 2);
                if (ohp != hp)
                    printf("HP CHANGED (%d != %d)\n", ohp,
hp);
                ohp = hp;
                if (!(i % 1000))
                    printf(".");
                fflush(stdout);
        }
        printf("Press <RETURN>... ");
        getc(stdin);
}