psql: Show IP address in \conninfo

When hostaddr is given, the actual IP address that psql is connected to
can be totally unexpected for the given host.  The more verbose output
we now generate makes things clearer.  Since the "host" and "hostaddr"
parts of the conninfo could come from different sources (say, one of
them is in the service specification or a URI-style conninfo and the
other is not), this is not as silly as it may first appear.  This is
also definitely useful if the hostname resolves to multiple addresses.

Author: Fabien Coelho
Reviewed-by: Pavel Stehule, Arthur Zakirov
Discussion: https://postgr.es/m/alpine.DEB.2.21.1810261532380.27686@lancre
	https://postgr.es/m/alpine.DEB.2.21.1808201323020.13832@lancre

doc/src/sgml/libpq.sgml

@@ -1735,6 +1735,36 @@ char *PQhost(const PGconn *conn);
      </listitem>
     </varlistentry>
 
+
+    <varlistentry id="libpq-pqhostaddr">
+     <term>
+      <function>PQhostaddr</function>
+      <indexterm>
+       <primary>PQhostaddr</primary>
+      </indexterm>
+     </term>
+
+     <listitem>
+      <para>
+       Returns the server IP address of the active connection.
+       This can be the address that a host name resolved to,
+       or an IP address provided through the <literal>hostaddr</literal>
+       parameter.
+<synopsis>
+char *PQhostaddr(const PGconn *conn);
+</synopsis>
+      </para>
+
+      <para>
+       <function>PQhostaddr</function> returns <symbol>NULL</symbol> if the
+       <parameter>conn</parameter> argument is <symbol>NULL</symbol>.
+       Otherwise, if there is an error producing the host information
+       (perhaps if the connection has not been fully established or
+       there was an error), it returns an empty string.
+      </para>
+     </listitem>
+    </varlistentry>
+
     <varlistentry id="libpq-pqport">
      <term>
       <function>PQport</function>

src/bin/psql/command.c

@@ -596,14 +596,30 @@ exec_command_conninfo(PsqlScanState scan_state, bool active_branch)
 		else
 		{
 			char	   *host = PQhost(pset.db);
+			char	   *hostaddr = PQhostaddr(pset.db);
 
-			/* If the host is an absolute path, the connection is via socket */
+			/*
+			 * If the host is an absolute path, the connection is via socket
+			 * unless overriden by hostaddr
+			 */
 			if (is_absolute_path(host))
-				printf(_("You are connected to database \"%s\" as user \"%s\" via socket in \"%s\" at port \"%s\".\n"),
-					   db, PQuser(pset.db), host, PQport(pset.db));
+			{
+				if (hostaddr && *hostaddr)
+					printf(_("You are connected to database \"%s\" as user \"%s\" on address \"%s\" at port \"%s\".\n"),
+						   db, PQuser(pset.db), hostaddr, PQport(pset.db));
+				else
+					printf(_("You are connected to database \"%s\" as user \"%s\" via socket in \"%s\" at port \"%s\".\n"),
+						   db, PQuser(pset.db), host, PQport(pset.db));
+			}
 			else
-				printf(_("You are connected to database \"%s\" as user \"%s\" on host \"%s\" at port \"%s\".\n"),
-					   db, PQuser(pset.db), host, PQport(pset.db));
+			{
+				if (hostaddr && *hostaddr && strcmp(host, hostaddr) != 0)
+					printf(_("You are connected to database \"%s\" as user \"%s\" on host \"%s\" (address \"%s\") at port \"%s\".\n"),
+						   db, PQuser(pset.db), host, hostaddr, PQport(pset.db));
+				else
+					printf(_("You are connected to database \"%s\" as user \"%s\" on host \"%s\" at port \"%s\".\n"),
+						   db, PQuser(pset.db), host, PQport(pset.db));
+			}
 			printSSLInfo();
 		}
 	}
@@ -2854,6 +2870,7 @@ do_connect(enum trivalue reuse_previous_specification,
 	PGconn	   *o_conn = pset.db,
 			   *n_conn;
 	char	   *password = NULL;
+	char	   *hostaddr = NULL;
 	bool		keep_password;
 	bool		has_connection_string;
 	bool		reuse_previous;
@@ -2894,12 +2911,27 @@ do_connect(enum trivalue reuse_previous_specification,
 	}
 
 	/* grab missing values from the old connection */
-	if (!user && reuse_previous)
-		user = PQuser(o_conn);
-	if (!host && reuse_previous)
-		host = PQhost(o_conn);
-	if (!port && reuse_previous)
-		port = PQport(o_conn);
+	if (reuse_previous)
+	{
+		if (!user)
+			user = PQuser(o_conn);
+		if (host && strcmp(host, PQhost(o_conn)) == 0)
+		{
+			/*
+			 * if we are targetting the same host, reuse its hostaddr for
+			 * consistency
+			 */
+			hostaddr = PQhostaddr(o_conn);
+		}
+		if (!host)
+		{
+			host = PQhost(o_conn);
+			/* also set hostaddr for consistency */
+			hostaddr = PQhostaddr(o_conn);
+		}
+		if (!port)
+			port = PQport(o_conn);
+	}
 
 	/*
 	 * Any change in the parameters read above makes us discard the password.
@@ -2961,13 +2993,18 @@ do_connect(enum trivalue reuse_previous_specification,
 
 	while (true)
 	{
-#define PARAMS_ARRAY_SIZE	8
+#define PARAMS_ARRAY_SIZE	9
 		const char **keywords = pg_malloc(PARAMS_ARRAY_SIZE * sizeof(*keywords));
 		const char **values = pg_malloc(PARAMS_ARRAY_SIZE * sizeof(*values));
 		int			paramnum = -1;
 
 		keywords[++paramnum] = "host";
 		values[paramnum] = host;
+		if (hostaddr && *hostaddr)
+		{
+			keywords[++paramnum] = "hostaddr";
+			values[paramnum] = hostaddr;
+		}
 		keywords[++paramnum] = "port";
 		values[paramnum] = port;
 		keywords[++paramnum] = "user";
@@ -3071,14 +3108,27 @@ do_connect(enum trivalue reuse_previous_specification,
 			param_is_newly_set(PQport(o_conn), PQport(pset.db)))
 		{
 			char	   *host = PQhost(pset.db);
+			char	   *hostaddr = PQhostaddr(pset.db);
 
 			/* If the host is an absolute path, the connection is via socket */
 			if (is_absolute_path(host))
-				printf(_("You are now connected to database \"%s\" as user \"%s\" via socket in \"%s\" at port \"%s\".\n"),
-					   PQdb(pset.db), PQuser(pset.db), host, PQport(pset.db));
+			{
+				if (hostaddr && *hostaddr)
+					printf(_("You are now connected to database \"%s\" as user \"%s\" on address \"%s\" at port \"%s\".\n"),
+						   PQdb(pset.db), PQuser(pset.db), hostaddr, PQport(pset.db));
+				else
+					printf(_("You are now connected to database \"%s\" as user \"%s\" via socket in \"%s\" at port \"%s\".\n"),
+						   PQdb(pset.db), PQuser(pset.db), host, PQport(pset.db));
+			}
 			else
-				printf(_("You are now connected to database \"%s\" as user \"%s\" on host \"%s\" at port \"%s\".\n"),
-					   PQdb(pset.db), PQuser(pset.db), host, PQport(pset.db));
+			{
+				if (hostaddr && *hostaddr && strcmp(host, hostaddr) != 0)
+					printf(_("You are now connected to database \"%s\" as user \"%s\" on host \"%s\" (address \"%s\") at port \"%s\".\n"),
+						   PQdb(pset.db), PQuser(pset.db), host, hostaddr, PQport(pset.db));
+				else
+					printf(_("You are now connected to database \"%s\" as user \"%s\" on host \"%s\" at port \"%s\".\n"),
+						   PQdb(pset.db), PQuser(pset.db), host, PQport(pset.db));
+			}
 		}
 		else
 			printf(_("You are now connected to database \"%s\" as user \"%s\".\n"),

src/interfaces/libpq/exports.txt

@@ -173,3 +173,4 @@ PQsetErrorContextVisibility 170
 PQresultVerboseErrorMessage 171
 PQencryptPasswordConn     172
 PQresultMemorySize        173
+PQhostaddr                174

src/interfaces/libpq/fe-connect.c

@@ -1471,6 +1471,39 @@ connectNoDelay(PGconn *conn)
 	return 1;
 }
 
+/* ----------
+ * Write currently connected IP address into host_addr (of len host_addr_len).
+ * If unable to, set it to the empty string.
+ * ----------
+ */
+static void
+getHostaddr(PGconn *conn, char *host_addr, int host_addr_len)
+{
+	struct sockaddr_storage *addr = &conn->raddr.addr;
+
+	if (conn->connhost[conn->whichhost].type == CHT_HOST_ADDRESS)
+		strlcpy(host_addr, conn->connhost[conn->whichhost].hostaddr, host_addr_len);
+	else if (addr->ss_family == AF_INET)
+	{
+		if (inet_net_ntop(AF_INET,
+						  &((struct sockaddr_in *) addr)->sin_addr.s_addr,
+						  32,
+						  host_addr, host_addr_len) == NULL)
+			host_addr[0] = '\0';
+	}
+#ifdef HAVE_IPV6
+	else if (addr->ss_family == AF_INET6)
+	{
+		if (inet_net_ntop(AF_INET6,
+						  &((struct sockaddr_in6 *) addr)->sin6_addr.s6_addr,
+						  128,
+						  host_addr, host_addr_len) == NULL)
+			host_addr[0] = '\0';
+	}
+#endif
+	else
+		host_addr[0] = '\0';
+}
 
 /* ----------
  * connectFailureMessage -
@@ -1504,34 +1537,12 @@ connectFailureMessage(PGconn *conn, int errorno)
 		char		host_addr[NI_MAXHOST];
 		const char *displayed_host;
 		const char *displayed_port;
-		struct sockaddr_storage *addr = &conn->raddr.addr;
 
 		/*
 		 * Optionally display the network address with the hostname. This is
 		 * useful to distinguish between IPv4 and IPv6 connections.
 		 */
-		if (conn->connhost[conn->whichhost].type == CHT_HOST_ADDRESS)
-			strlcpy(host_addr, conn->connhost[conn->whichhost].hostaddr, NI_MAXHOST);
-		else if (addr->ss_family == AF_INET)
-		{
-			if (inet_net_ntop(AF_INET,
-							  &((struct sockaddr_in *) addr)->sin_addr.s_addr,
-							  32,
-							  host_addr, sizeof(host_addr)) == NULL)
-				strcpy(host_addr, "???");
-		}
-#ifdef HAVE_IPV6
-		else if (addr->ss_family == AF_INET6)
-		{
-			if (inet_net_ntop(AF_INET6,
-							  &((struct sockaddr_in6 *) addr)->sin6_addr.s6_addr,
-							  128,
-							  host_addr, sizeof(host_addr)) == NULL)
-				strcpy(host_addr, "???");
-		}
-#endif
-		else
-			strcpy(host_addr, "???");
+		getHostaddr(conn, host_addr, NI_MAXHOST);
 
 		/* To which host and port were we actually connecting? */
 		if (conn->connhost[conn->whichhost].type == CHT_HOST_ADDRESS)
@@ -1548,14 +1559,14 @@ connectFailureMessage(PGconn *conn, int errorno)
 		 * looked-up IP address.
 		 */
 		if (conn->connhost[conn->whichhost].type != CHT_HOST_ADDRESS &&
+			strlen(host_addr) > 0 &&
 			strcmp(displayed_host, host_addr) != 0)
 			appendPQExpBuffer(&conn->errorMessage,
 							  libpq_gettext("could not connect to server: %s\n"
 											"\tIs the server running on host \"%s\" (%s) and accepting\n"
 											"\tTCP/IP connections on port %s?\n"),
 							  SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)),
-							  displayed_host,
-							  host_addr,
+							  displayed_host, host_addr,
 							  displayed_port);
 		else
 			appendPQExpBuffer(&conn->errorMessage,
@@ -2286,6 +2297,7 @@ keep_going:						/* We will come back to here until there is
 				 */
 				{
 					struct addrinfo *addr_cur = conn->addr_cur;
+					char		host_addr[NI_MAXHOST];
 
 					/*
 					 * Advance to next possible host, if we've tried all of
@@ -2302,6 +2314,21 @@ keep_going:						/* We will come back to here until there is
 						   addr_cur->ai_addrlen);
 					conn->raddr.salen = addr_cur->ai_addrlen;
 
+					/* set connip */
+					if (conn->connip != NULL)
+					{
+						free(conn->connip);
+						conn->connip = NULL;
+					}
+
+					getHostaddr(conn, host_addr, NI_MAXHOST);
+					if (strlen(host_addr) > 0)
+						conn->connip = strdup(host_addr);
+					/*
+					 * purposely ignore strdup failure; not a big problem if
+					 * it fails anyway.
+					 */
+
 					conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
 					if (conn->sock == PGINVALID_SOCKET)
 					{
@@ -3665,6 +3692,8 @@ freePGconn(PGconn *conn)
 		free(conn->sslcompression);
 	if (conn->requirepeer)
 		free(conn->requirepeer);
+	if (conn->connip)
+		free(conn->connip);
 #if defined(ENABLE_GSS) || defined(ENABLE_SSPI)
 	if (conn->krbsrvname)
 		free(conn->krbsrvname);
@@ -6172,6 +6201,25 @@ PQhost(const PGconn *conn)
 	return "";
 }
 
+char *
+PQhostaddr(const PGconn *conn)
+{
+	if (!conn)
+		return NULL;
+
+	if (conn->connhost != NULL)
+	{
+		if (conn->connhost[conn->whichhost].hostaddr != NULL &&
+			conn->connhost[conn->whichhost].hostaddr[0] != '\0')
+			return conn->connhost[conn->whichhost].hostaddr;
+
+		if (conn->connip != NULL)
+			return conn->connip;
+	}
+
+	return "";
+}
+
 char *
 PQport(const PGconn *conn)
 {

src/interfaces/libpq/libpq-fe.h

@@ -312,6 +312,7 @@ extern char *PQdb(const PGconn *conn);
 extern char *PQuser(const PGconn *conn);
 extern char *PQpass(const PGconn *conn);
 extern char *PQhost(const PGconn *conn);
+extern char *PQhostaddr(const PGconn *conn);
 extern char *PQport(const PGconn *conn);
 extern char *PQtty(const PGconn *conn);
 extern char *PQoptions(const PGconn *conn);

src/interfaces/libpq/libpq-int.h

@@ -397,6 +397,7 @@ struct pg_conn
 	int			nconnhost;		/* # of hosts named in conn string */
 	int			whichhost;		/* host we're currently trying/connected to */
 	pg_conn_host *connhost;		/* details about each named host */
+	char	   *connip;			/* IP address for current network connection */
 
 	/* Connection data */
 	pgsocket	sock;			/* FD for socket, PGINVALID_SOCKET if