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authorUlrich Drepper <drepper@redhat.com>2007-11-23 03:03:59 +0000
committerUlrich Drepper <drepper@redhat.com>2007-11-23 03:03:59 +0000
commit5c3a3dba227808f16a1dc2676c9fc49f66945b08 (patch)
tree1fd6c6ff9cecfe31a6cf215d31bf28e54c198c30 /resolv
parent8588312396635a2c5f13bd235217597456e0e4d2 (diff)
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[BZ #5375]
* resolv/res_hconf.c (_res_hconf_reorder_addrs): Fix locking when initializing interface list.
Diffstat (limited to 'resolv')
-rw-r--r--resolv/res_hconf.c80
1 files changed, 44 insertions, 36 deletions
diff --git a/resolv/res_hconf.c b/resolv/res_hconf.c
index c53b809ef7..25f7397927 100644
--- a/resolv/res_hconf.c
+++ b/resolv/res_hconf.c
@@ -377,9 +377,6 @@ static struct netaddr
} u;
} *ifaddrs);
-/* We need to protect the dynamic buffer handling. */
-__libc_lock_define_initialized (static, lock);
-
/* Reorder addresses returned in a hostent such that the first address
is an address on the local subnet, if there is such an address.
Otherwise, nothing is changed.
@@ -393,6 +390,8 @@ _res_hconf_reorder_addrs (struct hostent *hp)
int i, j;
/* Number of interfaces. */
static int num_ifs = -1;
+ /* We need to protect the dynamic buffer handling. */
+ __libc_lock_define_initialized (static, lock);
/* Only reorder if we're supposed to. */
if ((_res_hconf.flags & HCONF_FLAG_REORDER) == 0)
@@ -411,8 +410,6 @@ _res_hconf_reorder_addrs (struct hostent *hp)
/* Initialize interface table. */
- num_ifs = 0;
-
/* The SIOCGIFNETMASK ioctl will only work on an AF_INET socket. */
sd = __socket (AF_INET, SOCK_DGRAM, 0);
if (sd < 0)
@@ -421,45 +418,56 @@ _res_hconf_reorder_addrs (struct hostent *hp)
/* Get lock. */
__libc_lock_lock (lock);
- /* Get a list of interfaces. */
- __ifreq (&ifr, &num, sd);
- if (!ifr)
- goto cleanup;
+ /* Recheck, somebody else might have done the work by done. */
+ if (num_ifs <= 0)
+ {
+ int new_num_ifs = 0;
- ifaddrs = malloc (num * sizeof (ifaddrs[0]));
- if (!ifaddrs)
- goto cleanup1;
+ /* Get a list of interfaces. */
+ __ifreq (&ifr, &num, sd);
+ if (!ifr)
+ goto cleanup;
- /* Copy usable interfaces in ifaddrs structure. */
- for (cur_ifr = ifr, i = 0; i < num; cur_ifr = __if_nextreq (cur_ifr), ++i)
- {
- if (cur_ifr->ifr_addr.sa_family != AF_INET)
- continue;
+ ifaddrs = malloc (num * sizeof (ifaddrs[0]));
+ if (!ifaddrs)
+ goto cleanup1;
- ifaddrs[num_ifs].addrtype = AF_INET;
- ifaddrs[num_ifs].u.ipv4.addr =
- ((struct sockaddr_in *) &cur_ifr->ifr_addr)->sin_addr.s_addr;
+ /* Copy usable interfaces in ifaddrs structure. */
+ for (cur_ifr = ifr, i = 0; i < num;
+ cur_ifr = __if_nextreq (cur_ifr), ++i)
+ {
+ if (cur_ifr->ifr_addr.sa_family != AF_INET)
+ continue;
- if (__ioctl (sd, SIOCGIFNETMASK, cur_ifr) < 0)
- continue;
+ ifaddrs[new_num_ifs].addrtype = AF_INET;
+ ifaddrs[new_num_ifs].u.ipv4.addr =
+ ((struct sockaddr_in *) &cur_ifr->ifr_addr)->sin_addr.s_addr;
- ifaddrs[num_ifs].u.ipv4.mask =
- ((struct sockaddr_in *) &cur_ifr->ifr_netmask)->sin_addr.s_addr;
+ if (__ioctl (sd, SIOCGIFNETMASK, cur_ifr) < 0)
+ continue;
- /* Now we're committed to this entry. */
- ++num_ifs;
- }
- /* Just keep enough memory to hold all the interfaces we want. */
- ifaddrs = realloc (ifaddrs, num_ifs * sizeof (ifaddrs[0]));
- assert (ifaddrs != NULL);
+ ifaddrs[new_num_ifs].u.ipv4.mask =
+ ((struct sockaddr_in *) &cur_ifr->ifr_netmask)->sin_addr.s_addr;
- cleanup1:
- __if_freereq (ifr, num);
+ /* Now we're committed to this entry. */
+ ++new_num_ifs;
+ }
+ /* Just keep enough memory to hold all the interfaces we want. */
+ ifaddrs = realloc (ifaddrs, new_num_ifs * sizeof (ifaddrs[0]));
+ assert (ifaddrs != NULL);
+
+ cleanup1:
+ __if_freereq (ifr, num);
+
+ cleanup:
+ /* Release lock, preserve error value, and close socket. */
+ save = errno;
+
+ num_ifs = new_num_ifs;
+
+ __libc_lock_unlock (lock);
+ }
- cleanup:
- /* Release lock, preserve error value, and close socket. */
- save = errno;
- __libc_lock_unlock (lock);
__close (sd);
}