From 305dad8388ea27b4d1bf1202e90ad6947ae0ab26 Mon Sep 17 00:00:00 2001

From: Pavan Balaji <balaji@anl.gov>

Date: Thu, 21 Jan 2016 17:01:42 -0600

Subject: [PATCH] hydra: improve localhost detection.

Be more forgiving for systems that do not resolve "localhost" or

equivalent names very well (e.g., they are not added to /etc/hosts).

Try them out, and if nothing works, fallback to "is not local" mode.

Thanks to Orion Poplawski <orion@cora.nwra.com> for the suggestion.

---

 src/pm/hydra/utils/sock/sock.c | 89 +++++++++++++++++++++++-------------------

 1 file changed, 48 insertions(+), 41 deletions(-)

diff --git a/src/pm/hydra/utils/sock/sock.c b/src/pm/hydra/utils/sock/sock.c

index 86b25077aac2..dc56c767f544 100644

--- a/src/pm/hydra/utils/sock/sock.c

+++ b/src/pm/hydra/utils/sock/sock.c

@@ -492,7 +492,7 @@ HYD_status HYDU_sock_get_iface_ip(char *iface, char **ip)

 HYD_status HYDU_sock_is_local(char *host, int *is_local)

 {

     struct hostent *ht;

-    char *host_ip = NULL, *local_ip = NULL, *lhost_ip = NULL;

+    char *host_ip = NULL, *lhost_ip = NULL;

     char lhost[MAX_HOSTNAME_LEN];

     struct sockaddr_in sa;

     struct ifaddrs *ifaddr, *ifa;

@@ -516,54 +516,63 @@ HYD_status HYDU_sock_is_local(char *host, int *is_local)

     /* STEP 1: If "host" matches the local host name, return */

     if (gethostname(lhost, MAX_HOSTNAME_LEN) < 0) {

-        HYDU_ERR_SETANDJUMP(status, HYD_INTERNAL_ERROR, "gethostname returned an error\n");

+        /* We can't figure out what my localhost name is.  *sigh*.  We

+         * could return an error here, but we will just punt it to the

+         * upper layer saying that we don't know if it is local.  We

+         * cannot try steps 2 and 3 either, since we don't have our

+         * local hostname. */

+        goto fn_exit;

     }

     else if (!strcmp(lhost, host)) {

         *is_local = 1;

         goto fn_exit;

     }

+    else {

+        /* we have our local hostname, but that does not match the

+         * provided hostname.  Let's try to get our remote IP address

+         * first.  If we can't get that, we can give up. */

+        /* If we are unable to resolve the remote host name, it need

+         * not be an error. It could mean that the user is using an

+         * alias for the hostname (e.g., an ssh config alias) */

+        if ((ht = gethostbyname(host)) == NULL)

+            goto fn_exit;

+        memset((char *) &sa, 0, sizeof(struct sockaddr_in));

+        memcpy(&sa.sin_addr, ht->h_addr_list[0], ht->h_length);

-    /* STEP 2: If the IP address associated with "host" and the IP address local

-     * host resolves to match, return */

-

-    if ((ht = gethostbyname(lhost)) == NULL) {

-        HYDU_ERR_SETANDJUMP(status, HYD_INTERNAL_ERROR, "gethostbyname error on %s: %s\n",

-                            lhost, hstrerror(h_errno));

+        /* Find the IP address of the host */

+        host_ip = HYDU_strdup((char *) inet_ntop(AF_INET, (const void *) &sa.sin_addr, buf,

+                                                 MAX_HOSTNAME_LEN));

+        HYDU_ASSERT(host_ip, status);

     }

-    memset((char *) &sa, 0, sizeof(struct sockaddr_in));

-    memcpy(&sa.sin_addr, ht->h_addr_list[0], ht->h_length);

-

-    /* Find the IP address of the host */

-    lhost_ip = HYDU_strdup((char *) inet_ntop(AF_INET, (const void *) &sa.sin_addr, buf,

-                                              MAX_HOSTNAME_LEN));

-    HYDU_ASSERT(lhost_ip, status);

+    /* OK, if we are here, we got the remote IP.  We have two ways of

+     * getting the local IP: gethostbyname or getifaddrs.  We'll try

+     * both.  */

-    /* If we are unable to resolve the remote host name, it need not be an

-     * error. It could mean that the user is using an alias for the hostname

-     * (e.g., an ssh config alias) */

-    if ((ht = gethostbyname(host)) == NULL)

-        goto fn_exit;

+    /* STEP 2: Let's try the gethostbyname model */

-    memset((char *) &sa, 0, sizeof(struct sockaddr_in));

-    memcpy(&sa.sin_addr, ht->h_addr_list[0], ht->h_length);

+    if ((ht = gethostbyname(lhost))) {

+        memset((char *) &sa, 0, sizeof(struct sockaddr_in));

+        memcpy(&sa.sin_addr, ht->h_addr_list[0], ht->h_length);

-    /* Find the IP address of the host */

-    host_ip = HYDU_strdup((char *) inet_ntop(AF_INET, (const void *) &sa.sin_addr, buf,

-                                             MAX_HOSTNAME_LEN));

-    HYDU_ASSERT(host_ip, status);

+        /* Find the IP address of the host */

+        lhost_ip = HYDU_strdup((char *) inet_ntop(AF_INET, (const void *) &sa.sin_addr, buf,

+                                                  MAX_HOSTNAME_LEN));

+        HYDU_ASSERT(lhost_ip, status);

-    /* See if the IP address of the hostname we got matches the IP address

-     * to which the local host resolves */

-    if (!strcmp(lhost_ip, host_ip)) {

-        *is_local = 1;

-        goto fn_exit;

+        /* See if the IP address of the hostname we got matches the IP

+         * address to which the local host resolves */

+        if (!strcmp(lhost_ip, host_ip)) {

+            *is_local = 1;

+            goto fn_exit;

+        }

     }

+    /* Either gethostbyname didn't resolve or we didn't find a match.

+     * Either way, let's try the getifaddr model. */

-    /* STEP 3: Find all local IP addresses and try to match the host IP

-     * with it. */

+    /* STEP 3: Let's try the getifaddr model */

     if (getifaddrs(&ifaddr) == -1)

         HYDU_ERR_SETANDJUMP(status, HYD_INTERNAL_ERROR, "getifaddrs failed\n");

@@ -573,21 +582,21 @@ HYD_status HYDU_sock_is_local(char *host, int *is_local)

         if (ifa->ifa_addr && ifa->ifa_addr->sa_family == AF_INET) {

             struct sockaddr_in *sa_ptr = (struct sockaddr_in *) ifa->ifa_addr;

-            local_ip = HYDU_strdup((char *)

+            lhost_ip = HYDU_strdup((char *)

                                    inet_ntop(AF_INET, (const void *) &(sa_ptr->sin_addr), buf,

                                              MAX_HOSTNAME_LEN));

-            HYDU_ASSERT(local_ip, status);

+            HYDU_ASSERT(lhost_ip, status);

-            /* STEP 3: For each local IP address, see if it matches the "host"

+            /* For each local IP address, see if it matches the "host"

              * IP address */

-            if (!strcmp(host_ip, local_ip)) {

+            if (!strcmp(host_ip, lhost_ip)) {

                 *is_local = 1;

                 freeifaddrs(ifaddr);

                 goto fn_exit;

             }

-            HYDU_FREE(local_ip);

-            local_ip = NULL;

+            HYDU_FREE(lhost_ip);

+            lhost_ip = NULL;

         }

     }

@@ -596,8 +605,6 @@ HYD_status HYDU_sock_is_local(char *host, int *is_local)

   fn_exit:

     if (host_ip)

         HYDU_FREE(host_ip);

-    if (local_ip)

-        HYDU_FREE(local_ip);

     if (lhost_ip)

         HYDU_FREE(lhost_ip);

     return status;

-- 

1.9.1