Save and re-use resolved address for given hostname
If tcp_connect is called with the same server name, don't look up the address again. This avoids connecting to other servers when using a round-robin RDS farm name, as recommended by Microsoft. This introduces a backwards-incompatible change. If rdesktop was reconnecting because the user was moving between networks and the server is no longer reachable on the same address, the user must re-start rdesktop to reach their server.
This commit is contained in:
Karl Mikaelsson
parent
8c9c52abd2
commit
d6c99bf599
154
tcp.c
154
tcp.c
@ -58,6 +58,13 @@
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#define STREAM_COUNT 1
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#endif
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#ifdef IPv6
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static struct addrinfo *g_server_address = NULL;
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#else
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struct sockaddr_in *g_server_address = NULL;
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#endif
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static char *g_last_server_name = NULL;
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static RD_BOOL g_ssl_initialized = False;
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static SSL *g_ssl = NULL;
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static SSL_CTX *g_ssl_ctx = NULL;
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@ -416,47 +423,85 @@ tcp_tls_get_server_pubkey(STREAM s)
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return (s->size != 0);
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}
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/* Establish a connection on the TCP layer */
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/* Helper function to determine if rdesktop should resolve hostnames again or not */
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static RD_BOOL
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tcp_connect_resolve_hostname(const char *server)
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{
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return (g_server_address == NULL ||
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g_last_server_name == NULL ||
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strcmp(g_last_server_name, server) != 0);
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}
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/* Establish a connection on the TCP layer
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This function tries to avoid resolving any server address twice. The
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official Windows 2008 documentation states that the windows farm name
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should be a round-robin DNS entry containing all the terminal servers
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in the farm. When connected to the farm address, if we look up the
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address again when reconnecting (for any reason) we risk reconnecting
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to a different server in the farm.
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*/
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RD_BOOL
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tcp_connect(char *server)
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{
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socklen_t option_len;
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uint32 option_value;
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int i;
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char buf[NI_MAXHOST];
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#ifdef IPv6
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int n;
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struct addrinfo hints, *res, *ressave;
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struct addrinfo hints, *res, *addr;
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struct sockaddr *oldaddr;
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char tcp_port_rdp_s[10];
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snprintf(tcp_port_rdp_s, 10, "%d", g_tcp_port_rdp);
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memset(&hints, 0, sizeof(struct addrinfo));
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hints.ai_family = AF_UNSPEC;
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hints.ai_socktype = SOCK_STREAM;
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if ((n = getaddrinfo(server, tcp_port_rdp_s, &hints, &res)))
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if (tcp_connect_resolve_hostname(server))
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{
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logger(Core, Error, "tcp_connect(), getaddrinfo() failed: %s", gai_strerror(n));
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return False;
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}
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snprintf(tcp_port_rdp_s, 10, "%d", g_tcp_port_rdp);
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ressave = res;
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g_sock = -1;
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while (res)
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{
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g_sock = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
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if (!(g_sock < 0))
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memset(&hints, 0, sizeof(struct addrinfo));
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hints.ai_family = AF_UNSPEC;
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hints.ai_socktype = SOCK_STREAM;
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if ((n = getaddrinfo(server, tcp_port_rdp_s, &hints, &res)))
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{
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if (connect(g_sock, res->ai_addr, res->ai_addrlen) == 0)
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break;
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TCP_CLOSE(g_sock);
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g_sock = -1;
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logger(Core, Error, "tcp_connect(), getaddrinfo() failed: %s", gai_strerror(n));
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return False;
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}
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res = res->ai_next;
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}
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freeaddrinfo(ressave);
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else
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{
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res = g_server_address;
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}
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g_sock = -1;
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for (addr = res; addr != NULL; addr = addr->ai_next)
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{
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g_sock = socket(addr->ai_family, addr->ai_socktype, addr->ai_protocol);
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if (g_sock < 0)
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{
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logger(Core, Debug, "tcp_connect(), socket() failed: %s", TCP_STRERROR);
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continue;
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}
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n = getnameinfo(addr->ai_addr, addr->ai_addrlen, buf, sizeof(buf), NULL, 0, NI_NUMERICHOST);
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if (n != 0)
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{
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logger(Core, Error, "tcp_connect(), getnameinfo() failed: %s", gai_strerror(n));
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return False;
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}
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logger(Core, Debug, "tcp_connect(), trying %s (%s)", server, buf);
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if (connect(g_sock, addr->ai_addr, addr->ai_addrlen) == 0)
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break;
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TCP_CLOSE(g_sock);
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g_sock = -1;
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}
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if (g_sock == -1)
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{
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@ -464,19 +509,50 @@ tcp_connect(char *server)
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return False;
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}
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#else /* no IPv6 support */
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/* Save server address for later use, if we haven't already. */
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struct hostent *nslookup;
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struct sockaddr_in servaddr;
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if ((nslookup = gethostbyname(server)) != NULL)
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if (g_server_address == NULL)
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{
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memcpy(&servaddr.sin_addr, nslookup->h_addr, sizeof(servaddr.sin_addr));
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g_server_address = xmalloc(sizeof(struct addrinfo));
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g_server_address->ai_addr = xmalloc(sizeof(struct sockaddr_storage));
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}
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else if ((servaddr.sin_addr.s_addr = inet_addr(server)) == INADDR_NONE)
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if (g_server_address != addr)
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{
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logger(Core, Error, "tcp_connect(), unable to resolve host '%s'", server);
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return False;
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/* don't overwrite ptr to allocated sockaddr */
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oldaddr = g_server_address->ai_addr;
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memcpy(g_server_address, addr, sizeof(struct addrinfo));
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g_server_address->ai_addr = oldaddr;
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memcpy(g_server_address->ai_addr, addr->ai_addr, addr->ai_addrlen);
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g_server_address->ai_canonname = NULL;
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g_server_address->ai_next = NULL;
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freeaddrinfo(res);
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}
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#else /* no IPv6 support */
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struct hostent *nslookup = NULL;
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if (tcp_connect_resolve_hostname(server))
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{
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if (g_server_address != NULL)
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xfree(g_server_address);
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g_server_address = xmalloc(sizeof(struct sockaddr_in));
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g_server_address->sin_family = AF_INET;
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g_server_address->sin_port = htons((uint16) g_tcp_port_rdp);
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if ((nslookup = gethostbyname(server)) != NULL)
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{
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memcpy(&g_server_address->sin_addr, nslookup->h_addr,
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sizeof(g_server_address->sin_addr));
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}
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else if ((g_server_address->sin_addr.s_addr = inet_addr(server)) == INADDR_NONE)
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{
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logger(Core, Error, "tcp_connect(), unable to resolve host '%s'", server);
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return False;
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}
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}
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if ((g_sock = socket(AF_INET, SOCK_STREAM, 0)) < 0)
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@ -485,10 +561,12 @@ tcp_connect(char *server)
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return False;
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}
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servaddr.sin_family = AF_INET;
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servaddr.sin_port = htons((uint16) g_tcp_port_rdp);
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logger(Core, Debug, "tcp_connect(), trying %s (%s)",
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server, inet_ntop(g_server_address->sin_family,
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&g_server_address->sin_addr,
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buf, sizeof(buf)));
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if (connect(g_sock, (struct sockaddr *) &servaddr, sizeof(struct sockaddr)) < 0)
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if (connect(g_sock, (struct sockaddr *) g_server_address, sizeof(struct sockaddr)) < 0)
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{
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if (!g_reconnect_loop)
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logger(Core, Error, "tcp_connect(), connect() failed: %s", TCP_STRERROR);
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@ -524,6 +602,10 @@ tcp_connect(char *server)
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g_out[i].data = (uint8 *) xmalloc(g_out[i].size);
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}
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/* After successful connect: update the last server name */
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if (g_last_server_name)
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xfree(g_last_server_name);
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g_last_server_name = strdup(server);
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return True;
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}
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