client: reconnect with multiple addresses

Allow multiple hostnames/addresses separated by comma to be specified
with the -h option. Hostnames are resolved to up to 16 addresses. When
connecting to an address fails or no reply is received, try the next
address in the list.

Set the default value for the -h option to 127.0.0.1,::1.

Makefile.in

@@ -44,7 +44,7 @@ OBJS = array.o cmdparse.o conf.o local.o logging.o main.o memory.o \
 
 EXTRA_OBJS=@EXTRA_OBJECTS@
 
-CLI_OBJS = client.o cmdparse.o getdate.o memory.o nameserv.o \
+CLI_OBJS = array.o client.o cmdparse.o getdate.o memory.o nameserv.o \
            pktlength.o util.o $(HASH_OBJ)
 
 ALL_OBJS = $(OBJS) $(EXTRA_OBJS) $(CLI_OBJS)

chrony.texi.in

@@ -3252,9 +3252,9 @@ Chronyc supports the following command line options.
 @item -v
 Displays the version number of chronyc on the terminal, and exists.
 @item -h <host>
-This option allows the user to specify which host running the
+This option allows the user to specify which host (or comma-separated list of
-@code{chronyd} program is to be contacted.  This allows for remote
+addresses) running the @code{chronyd} program is to be contacted.  This allows
-configuration, without having to ssh to the other host first.
+for remote configuration, without having to ssh to the other host first.
 
 The default is to contact @code{chronyd} running on the same host as
 that where chronyc is being run.

chronyc.1.in

@@ -24,7 +24,7 @@ A summary of the options supported by \fBchronyc\fR is included below.
 
 .TP
 \fB\-h\fR \fIhostname\fR
-specify hostname (default 127.0.0.1)
+specify hostname or comma-separated list of addresses (default 127.0.0.1,::1)
 .TP
 \fB\-p\fR \fIport-number\fR
 specify port-number

client.c

@@ -30,6 +30,7 @@
 
 #include "sysincl.h"
 
+#include "array.h"
 #include "candm.h"
 #include "logging.h"
 #include "memory.h"
@@ -60,7 +61,9 @@ union sockaddr_all {
   struct sockaddr sa;
 };
 
-static int sock_fd;
+static ARR_Instance sockaddrs;
+
+static int sock_fd = -1;
 
 static int quit = 0;
 
@@ -129,65 +132,118 @@ read_line(void)
 }
 
 /* ================================================== */
-/* Initialise the socket used to talk to the daemon */
 
-static void
+#define MAX_ADDRESSES 16
-open_io(const char *hostname, int port)
+
+static ARR_Instance
+get_sockaddrs(const char *hostnames, int port)
 {
-  union sockaddr_all addr;
+  ARR_Instance addrs;
-  socklen_t addr_len;
+  char *hostname, *s1, *s2;
-  IPAddr ip;
+  IPAddr ip_addrs[MAX_ADDRESSES];
-  char *dir;
+  union sockaddr_all *addr;
+  int i;
+
+  addrs = ARR_CreateInstance(sizeof (union sockaddr_all));
+  s1 = Strdup(hostnames);
+
+  /* Parse the comma-separated list of hostnames */
+  for (hostname = s1; hostname && *hostname; hostname = s2) {
+    s2 = strchr(hostname, ',');
+    if (s2)
+      *s2++ = '\0';
 
     /* hostname starting with / is considered a path of Unix domain socket */
     if (hostname[0] == '/') {
-    if (snprintf(addr.un.sun_path, sizeof (addr.un.sun_path), "%s", hostname) >=
+      addr = (union sockaddr_all *)ARR_GetNewElement(addrs);
-        sizeof (addr.un.sun_path))
+      if (snprintf(addr->un.sun_path, sizeof (addr->un.sun_path), "%s", hostname) >=
+          sizeof (addr->un.sun_path))
         LOG_FATAL(LOGF_Client, "Unix socket path too long");
-    addr.un.sun_family = AF_UNIX;
+      addr->un.sun_family = AF_UNIX;
-    addr_len = sizeof (addr.un);
     } else {
-    /* Note, this call could block for a while */
+      if (DNS_Name2IPAddress(hostname, ip_addrs, MAX_ADDRESSES) != DNS_Success) {
-    if (DNS_Name2IPAddress(hostname, &ip, 1) != DNS_Success) {
+        DEBUG_LOG(LOGF_Client, "Could not get IP address for %s", hostname);
-      LOG_FATAL(LOGF_Client, "Could not get IP address for %s", hostname);
+        break;
       }
 
-    addr_len = UTI_IPAndPortToSockaddr(&ip, port, &addr.sa);
+      for (i = 0; i < MAX_ADDRESSES && ip_addrs[i].family != IPADDR_UNSPEC; i++) {
+        addr = (union sockaddr_all *)ARR_GetNewElement(addrs);
+        UTI_IPAndPortToSockaddr(&ip_addrs[i], port, (struct sockaddr *)addr);
+        DEBUG_LOG(LOGF_Client, "Resolved %s to %s", hostname, UTI_IPToString(&ip_addrs[i]));
+      }
+    }
   }
 
-  sock_fd = socket(addr.sa.sa_family, SOCK_DGRAM, 0);
+  Free(s1);
+  return addrs;
+}
+
+/* ================================================== */
+/* Initialise the socket used to talk to the daemon */
+
+static int
+prepare_socket(union sockaddr_all *addr)
+{
+  socklen_t addr_len;
+  char *dir;
+
+  switch (addr->sa.sa_family) {
+    case AF_UNIX:
+      addr_len = sizeof (addr->un);
+      break;
+    case AF_INET:
+      addr_len = sizeof (addr->in4);
+      break;
+#ifdef FEAT_IPV6
+    case AF_INET6:
+      addr_len = sizeof (addr->in6);
+      break;
+#endif
+    default:
+      assert(0);
+  }
+
+  sock_fd = socket(addr->sa.sa_family, SOCK_DGRAM, 0);
 
   if (sock_fd < 0) {
-    LOG_FATAL(LOGF_Client, "Could not create socket : %s", strerror(errno));
+    DEBUG_LOG(LOGF_Client, "Could not create socket : %s", strerror(errno));
+    return 0;
   }
 
-  if (connect(sock_fd, &addr.sa, addr_len) < 0) {
+  if (connect(sock_fd, &addr->sa, addr_len) < 0) {
-    LOG_FATAL(LOGF_Client, "Could not connect socket : %s", strerror(errno));
+    DEBUG_LOG(LOGF_Client, "Could not connect socket : %s", strerror(errno));
+    return 0;
   }
 
-  if (addr.sa.sa_family == AF_UNIX) {
+  if (addr->sa.sa_family == AF_UNIX) {
+    struct sockaddr_un sun;
+
     /* Construct path of our socket.  Use the same directory as the server
        socket and include our process ID to allow multiple chronyc instances
        running at the same time. */
-    dir = UTI_PathToDir(hostname);
+    dir = UTI_PathToDir(addr->un.sun_path);
-    if (snprintf(addr.un.sun_path, sizeof (addr.un.sun_path),
+    if (snprintf(sun.sun_path, sizeof (sun.sun_path),
-             "%s/chronyc.%d.sock", dir, getpid()) >= sizeof (addr.un.sun_path))
+                 "%s/chronyc.%d.sock", dir, getpid()) >= sizeof (sun.sun_path))
       LOG_FATAL(LOGF_Client, "Unix socket path too long");
     Free(dir);
 
-    addr.un.sun_family = AF_UNIX;
+    sun.sun_family = AF_UNIX;
-    unlink(addr.un.sun_path);
+    unlink(sun.sun_path);
 
     /* Bind the socket to the path */
-    if (bind(sock_fd, &addr.sa, sizeof (addr.un)) < 0) {
+    if (bind(sock_fd, (struct sockaddr *)&sun, sizeof (sun)) < 0) {
-      LOG_FATAL(LOGF_Client, "Could not bind socket : %s", strerror(errno));
+      DEBUG_LOG(LOGF_Client, "Could not bind socket : %s", strerror(errno));
+      return 0;
     }
 
     /* Allow server without root privileges to send replies to our socket */
-    if (chmod(addr.un.sun_path, 0666) < 0) {
+    if (chmod(sun.sun_path, 0666) < 0) {
-      LOG_FATAL(LOGF_Client, "Could not change socket permissions : %s", strerror(errno));
+      DEBUG_LOG(LOGF_Client, "Could not change socket permissions : %s", strerror(errno));
+      return 0;
     }
   }
+
+  return 1;
 }
 
 /* ================================================== */
@@ -198,6 +254,9 @@ close_io(void)
   union sockaddr_all addr;
   socklen_t addr_len = sizeof (addr);
 
+  if (sock_fd < 0)
+    return;
+
   /* Remove our Unix domain socket */
   if (getsockname(sock_fd, &addr.sa, &addr_len) < 0)
     LOG_FATAL(LOGF_Client, "getsockname() failed : %s", strerror(errno));
@@ -206,6 +265,36 @@ close_io(void)
     unlink(addr.un.sun_path);
 
   close(sock_fd);
+  sock_fd = -1;
+}
+
+/* ================================================== */
+
+static int
+open_io(void)
+{
+  static unsigned int address_index = 0;
+  union sockaddr_all *addr;
+
+  /* If a socket is already opened, close it and try the next address */
+  if (sock_fd >= 0) {
+    close_io();
+    address_index++;
+  }
+
+  /* Find an address for which a socket can be opened and connected */
+  for (; address_index < ARR_GetSize(sockaddrs); address_index++) {
+    addr = (union sockaddr_all *)ARR_GetElement(sockaddrs, address_index);
+    DEBUG_LOG(LOGF_Client, "Opening connection to %s",
+              UTI_SockaddrToString(&addr->sa));
+
+    if (prepare_socket(addr))
+      return 1;
+
+    close_io();
+  }
+
+  return 0;
 }
 
 /* ================================================== */
@@ -1463,7 +1552,10 @@ request_reply(CMD_Request *request, CMD_Reply *reply, int requested_reply, int v
   int reply_auth_ok;
   int status;
 
-  if (!submit_request(request, reply, &reply_auth_ok)) {
+  while (!submit_request(request, reply, &reply_auth_ok)) {
+    /* Try connecting to other addresses before giving up */
+    if (open_io())
+      continue;
     printf("506 Cannot talk to daemon\n");
     return 0;
   }
@@ -2764,7 +2856,7 @@ main(int argc, char **argv)
 {
   char *line;
   const char *progname = argv[0];
-  const char *hostname = NULL;
+  const char *hostnames = NULL;
   const char *conf_file = DEFAULT_CONF_FILE;
   int ret = 1, multi = 0, auto_auth = 0, family = IPADDR_UNSPEC;
   int port = DEFAULT_CANDM_PORT;
@@ -2774,7 +2866,7 @@ main(int argc, char **argv)
     if (!strcmp(*argv, "-h")) {
       ++argv, --argc;
       if (*argv) {
-        hostname = *argv;
+        hostnames = *argv;
       }
     } else if (!strcmp(*argv, "-p")) {
       ++argv, --argc;
@@ -2827,8 +2919,8 @@ main(int argc, char **argv)
   
   DNS_SetAddressFamily(family);
 
-  if (!hostname) {
+  if (!hostnames) {
-    hostname = family == IPADDR_INET6 ? "::1" : "127.0.0.1";
+    hostnames = "127.0.0.1,::1";
 #ifdef FEAT_ASYNCDNS
     initial_timeout /= 10;
 #endif
@@ -2836,7 +2928,10 @@ main(int argc, char **argv)
 
   UTI_SetQuitSignalsHandler(signal_handler);
 
-  open_io(hostname, port);
+  sockaddrs = get_sockaddrs(hostnames, port);
+
+  if (!open_io())
+    LOG_FATAL(LOGF_Client, "Could not open connection to daemon");
 
   if (auto_auth) {
     ret = authenticate_from_config(conf_file);
@@ -2861,6 +2956,7 @@ main(int argc, char **argv)
   close_io();
 
   Free(password);
+  ARR_DestroyInstance(sockaddrs);
 
   return !ret;
 }