Fix: Set loopback adress in set_ip_addr if gethostbyname2 fails

Some systems may not have "localhost" defined in accordance with IETF
RFC 6761. According to this RFC, applications may recognize
"localhost" names as special and resolve to the appropriate loopback
address.

We choose to use the system name resolution API first to honor its
network configuration. If this fails, we resolve to the appropriate
loopback address. This is done to accomodate systems which may want to
start tracing before their network configured.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/common/uri.c b/src/common/uri.c
index fb61a5bbdc0c61138823fbae0fd143bffb328f65..58ffcbcd66de518c8fba4ee4c470609af5ec8491 100644 (file)
--- a/src/common/uri.c
+++ b/src/common/uri.c
@@ -29,6 +29,9 @@
 
 #include "uri.h"
 
+#define LOOPBACK_ADDR_IPV4 "127.0.0.1"
+#define LOOPBACK_ADDR_IPV6 "::1"
+
 enum uri_proto_code {
        P_NET, P_NET6, P_FILE, P_TCP, P_TCP6,
 };
@@ -115,14 +118,43 @@ static int set_ip_address(const char *addr, int af, char *dst, size_t size)
        if (ret < 1) {
                /* We consider the dst to be an hostname or an invalid IP char */
                record = lttng_gethostbyname2(addr, af);
-               if (record == NULL) {
+               if (record) {
+                       /* Translate IP to string */
+                       if (!inet_ntop(af, record->h_addr_list[0], dst, size)) {
+                               PERROR("inet_ntop");
+                               goto error;
+                       }
+               } else if (!strcmp(addr, "localhost") &&
+                               (af == AF_INET || af == AF_INET6)) {
+                       /*
+                        * Some systems may not have "localhost" defined in
+                        * accordance with IETF RFC 6761. According to this RFC,
+                        * applications may recognize "localhost" names as
+                        * special and resolve to the appropriate loopback
+                        * address.
+                        *
+                        * We choose to use the system name resolution API first
+                        * to honor its network configuration. If this fails, we
+                        * resolve to the appropriate loopback address. This is
+                        * done to accomodate systems which may want to start
+                        * tracing before their network configured.
+                        */
+                       const char *loopback_addr = af == AF_INET ?
+                                       LOOPBACK_ADDR_IPV4 : LOOPBACK_ADDR_IPV6;
+                       const size_t loopback_addr_len = af == AF_INET ?
+                                       sizeof(LOOPBACK_ADDR_IPV4) :
+                                       sizeof(LOOPBACK_ADDR_IPV6);
+
+                       DBG2("Could not resolve localhost address, using fallback");
+                       if (loopback_addr_len > size) {
+                               ERR("Could not resolve localhost address; destination string is too short");
+                               goto error;
+                       }
+                       strcpy(dst, loopback_addr);
+               } else {
                        /* At this point, the IP or the hostname is bad */
-                       ERR("URI parse bad hostname %s for af %d", addr, af);
                        goto error;
                }
-
-               /* Translate IP to string */
-               (void) inet_ntop(af, record->h_addr_list[0], dst, size);
        } else {
                if (size > 0) {
                        strncpy(dst, addr, size);
@@ -131,10 +163,10 @@ static int set_ip_address(const char *addr, int af, char *dst, size_t size)
        }
 
        DBG2("IP address resolved to %s", dst);
-
        return 0;
 
 error:
+       ERR("URI parse bad hostname %s for af %d", addr, af);
        return -1;
 }