In ngx_inet.c, there is a code piece of function
“ngx_inet_resolve_host”. If I set u->one_addr to 1， but unfortunately
this hostname map to multiple IP addresses, such as
10.37.4.92 myhost
127.0.0.1 myhostin /etc/hosts.
h->h_addr_list will be 2 entries before NULL. Each of them will be
converted to human readable format and assigned to u->addrs[ i ].
However, when one_addr is set, u->addrs will be allocated ONLY ONE
ngx_addr_t mem. In this way, a mem crash is inevitable.
I set one_addr to 1 because I’m writing a custom module and want to
connect another server. Sadly the server is also running on the local
host with multiple IP in /etc/hosts. I want to connect the first IP
match that host name (10.37.4.92) because that server require a
non-lookback IP. I thought “one_addr” means “fetch the first found IP”.
But seems I was wrong.
Besides this, I insist alloc mem with “i”, but loop will h->h_addr_list
is very dangerous. Report an error is more suitable rather than leave a
time bomb.
Affected version: all versions!!!
----------------------------------------------related
coe---------------------------------------------
...
if (u->one_addr == 0) {
for (i = 0; h->h_addr_list[i] != NULL; i++) { /* void */ }
} else {
i = 1;
}
/* MP: ngx_shared_palloc() */
u->addrs = ngx_pcalloc(pool, i * sizeof(ngx_addr_t));
if (u->addrs == NULL) {
return NGX_ERROR;
}
u->naddrs = i;
for (i = 0; h->h_addr_list[ i ] != NULL; i++) {
sin = ngx_pcalloc(pool, sizeof(struct sockaddr_in));
if (sin == NULL) {
return NGX_ERROR;
}
sin->sin_family = AF_INET;
sin->sin_port = port;
sin->sin_addr.s_addr = *(in_addr_t *) (h->h_addr_list[ i
]);
u->addrs[ i ].sockaddr = (struct sockaddr *) sin;
u->addrs[ i ].socklen = sizeof(struct sockaddr_in);
len = NGX_INET_ADDRSTRLEN + sizeof(":65535") - 1;
p = ngx_pnalloc(pool, len);
if (p == NULL) {
return NGX_ERROR;
}
len = ngx_sock_ntop((struct sockaddr *) sin, p, len, 1);
u->addrs[ i ].name.len = len;
u->addrs[ i ].name.data = p;
}
...Posted at Nginx Forum: