Fix: Set loopback adress in set_ip_addr if gethostbyname2 fails
[lttng-tools.git] / src / common / uri.c
index fb61a5bbdc0c61138823fbae0fd143bffb328f65..58ffcbcd66de518c8fba4ee4c470609af5ec8491 100644 (file)
@@ -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;
 }
 
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