connect & http: support -4 and -6 switches for remote operations

Sometimes it is necessary to force IPv4-only or IPv6-only operation
on networks where name lookups may return a non-routable address and
stall remote operations.

The ssh(1) command has an equivalent switches which we may pass when
we run them.  There may be old ssh(1) implementations out there
which do not support these switches; they should report the
appropriate error in that case.

rsync support is untouched for now since it is deprecated and
scheduled to be removed.

Signed-off-by: Eric Wong <normalperson@yhbt.net>
Reviewed-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/fetch-options.txt

@@ -150,3 +150,11 @@ endif::git-pull[]
 	by default when it is attached to a terminal, unless -q
 	is specified. This flag forces progress status even if the
 	standard error stream is not directed to a terminal.
+
+-4::
+--ipv4::
+	Use IPv4 addresses only, ignoring IPv6 addresses.
+
+-6::
+--ipv6::
+	Use IPv6 addresses only, ignoring IPv4 addresses.

Documentation/git-push.txt

@@ -277,6 +277,13 @@ origin +master` to force a push to the `master` branch). See the
 	default is --verify, giving the hook a chance to prevent the
 	push.  With --no-verify, the hook is bypassed completely.
 
+-4::
+--ipv4::
+	Use IPv4 addresses only, ignoring IPv6 addresses.
+
+-6::
+--ipv6::
+	Use IPv6 addresses only, ignoring IPv4 addresses.
 
 include::urls-remotes.txt[]
 

builtin/clone.c

@@ -47,6 +47,7 @@ static const char *real_git_dir;
 static char *option_upload_pack = "git-upload-pack";
 static int option_verbosity;
 static int option_progress = -1;
+static enum transport_family family;
 static struct string_list option_config;
 static struct string_list option_reference;
 static int option_dissociate;
@@ -92,6 +93,10 @@ static struct option builtin_clone_options[] = {
 		   N_("separate git dir from working tree")),
 	OPT_STRING_LIST('c', "config", &option_config, N_("key=value"),
 			N_("set config inside the new repository")),
+	OPT_SET_INT('4', "ipv4", &family, N_("use IPv4 addresses only"),
+			TRANSPORT_FAMILY_IPV4),
+	OPT_SET_INT('6', "ipv6", &family, N_("use IPv6 addresses only"),
+			TRANSPORT_FAMILY_IPV6),
 	OPT_END()
 };
 
@@ -967,6 +972,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	remote = remote_get(option_origin);
 	transport = transport_get(remote, remote->url[0]);
 	transport_set_verbosity(transport, option_verbosity, option_progress);
+	transport->family = family;
 
 	path = get_repo_path(remote->url[0], &is_bundle);
 	is_local = option_local != 0 && path && !is_bundle;

builtin/fetch.c

@@ -37,6 +37,7 @@ static int prune = -1; /* unspecified */
 static int all, append, dry_run, force, keep, multiple, update_head_ok, verbosity;
 static int progress = -1, recurse_submodules = RECURSE_SUBMODULES_DEFAULT;
 static int tags = TAGS_DEFAULT, unshallow, update_shallow;
+static enum transport_family family;
 static const char *depth;
 static const char *upload_pack;
 static struct strbuf default_rla = STRBUF_INIT;
@@ -124,6 +125,10 @@ static struct option builtin_fetch_options[] = {
 		 N_("accept refs that update .git/shallow")),
 	{ OPTION_CALLBACK, 0, "refmap", NULL, N_("refmap"),
 	  N_("specify fetch refmap"), PARSE_OPT_NONEG, parse_refmap_arg },
+	OPT_SET_INT('4', "ipv4", &family, N_("use IPv4 addresses only"),
+			TRANSPORT_FAMILY_IPV4),
+	OPT_SET_INT('6', "ipv6", &family, N_("use IPv6 addresses only"),
+			TRANSPORT_FAMILY_IPV6),
 	OPT_END()
 };
 
@@ -861,6 +866,7 @@ static struct transport *prepare_transport(struct remote *remote)
 	struct transport *transport;
 	transport = transport_get(remote, NULL);
 	transport_set_verbosity(transport, verbosity, progress);
+	transport->family = family;
 	if (upload_pack)
 		set_option(transport, TRANS_OPT_UPLOADPACK, upload_pack);
 	if (keep)

builtin/push.c

@@ -23,6 +23,7 @@ static const char *receivepack;
 static int verbosity;
 static int progress = -1;
 static int recurse_submodules = RECURSE_SUBMODULES_DEFAULT;
+static enum transport_family family;
 
 static struct push_cas_option cas;
 
@@ -346,6 +347,7 @@ static int push_with_options(struct transport *transport, int flags)
 	unsigned int reject_reasons;
 
 	transport_set_verbosity(transport, verbosity, progress);
+	transport->family = family;
 
 	if (receivepack)
 		transport_set_option(transport,
@@ -565,6 +567,10 @@ int cmd_push(int argc, const char **argv, const char *prefix)
 		  0, "signed", &push_cert, "yes|no|if-asked", N_("GPG sign the push"),
 		  PARSE_OPT_OPTARG, option_parse_push_signed },
 		OPT_BIT(0, "atomic", &flags, N_("request atomic transaction on remote side"), TRANSPORT_PUSH_ATOMIC),
+		OPT_SET_INT('4', "ipv4", &family, N_("use IPv4 addresses only"),
+				TRANSPORT_FAMILY_IPV4),
+		OPT_SET_INT('6', "ipv6", &family, N_("use IPv6 addresses only"),
+				TRANSPORT_FAMILY_IPV6),
 		OPT_END()
 	};
 

connect.c

@@ -357,6 +357,10 @@ static int git_tcp_connect_sock(char *host, int flags)
 		port = "<none>";
 
 	memset(&hints, 0, sizeof(hints));
+	if (flags & CONNECT_IPV4)
+		hints.ai_family = AF_INET;
+	else if (flags & CONNECT_IPV6)
+		hints.ai_family = AF_INET6;
 	hints.ai_socktype = SOCK_STREAM;
 	hints.ai_protocol = IPPROTO_TCP;
 
@@ -783,6 +787,10 @@ struct child_process *git_connect(int fd[2], const char *url,
 			}
 
 			argv_array_push(&conn->args, ssh);
+			if (flags & CONNECT_IPV4)
+				argv_array_push(&conn->args, "-4");
+			else if (flags & CONNECT_IPV6)
+				argv_array_push(&conn->args, "-6");
 			if (tortoiseplink)
 				argv_array_push(&conn->args, "-batch");
 			if (port) {

connect.h

@@ -3,6 +3,8 @@
 
 #define CONNECT_VERBOSE       (1u << 0)
 #define CONNECT_DIAG_URL      (1u << 1)
+#define CONNECT_IPV4          (1u << 2)
+#define CONNECT_IPV6          (1u << 3)
 extern struct child_process *git_connect(int fd[2], const char *url, const char *prog, int flags);
 extern int finish_connect(struct child_process *conn);
 extern int git_connection_is_socket(struct child_process *conn);

http.c

@@ -11,6 +11,11 @@
 #include "gettext.h"
 #include "transport.h"
 
+#if LIBCURL_VERSION_NUM >= 0x070a08
+long int git_curl_ipresolve = CURL_IPRESOLVE_WHATEVER;
+#else
+long int git_curl_ipresolve;
+#endif
 int active_requests;
 int http_is_verbose;
 size_t http_post_buffer = 16 * LARGE_PACKET_MAX;
@@ -692,6 +697,10 @@ struct active_request_slot *get_active_slot(void)
 	curl_easy_setopt(slot->curl, CURLOPT_HTTPGET, 1);
 	curl_easy_setopt(slot->curl, CURLOPT_FAILONERROR, 1);
 	curl_easy_setopt(slot->curl, CURLOPT_RANGE, NULL);
+
+#if LIBCURL_VERSION_NUM >= 0x070a08
+	curl_easy_setopt(slot->curl, CURLOPT_IPRESOLVE, git_curl_ipresolve);
+#endif
 #ifdef LIBCURL_CAN_HANDLE_AUTH_ANY
 	curl_easy_setopt(slot->curl, CURLOPT_HTTPAUTH, http_auth_methods);
 #endif

http.h

@@ -106,6 +106,7 @@ extern void http_init(struct remote *remote, const char *url,
 		      int proactive_auth);
 extern void http_cleanup(void);
 
+extern long int git_curl_ipresolve;
 extern int active_requests;
 extern int http_is_verbose;
 extern size_t http_post_buffer;

remote-curl.c

@@ -119,6 +119,19 @@ static int set_option(const char *name, const char *value)
 		else
 			return -1;
 		return 0;
+
+#if LIBCURL_VERSION_NUM >= 0x070a08
+	} else if (!strcmp(name, "family")) {
+		if (!strcmp(value, "ipv4"))
+			git_curl_ipresolve = CURL_IPRESOLVE_V4;
+		else if (!strcmp(value, "ipv6"))
+			git_curl_ipresolve = CURL_IPRESOLVE_V6;
+		else if (!strcmp(value, "all"))
+			git_curl_ipresolve = CURL_IPRESOLVE_WHATEVER;
+		else
+			return -1;
+		return 0;
+#endif /* LIBCURL_VERSION_NUM >= 0x070a08 */
 	} else {
 		return 1 /* unsupported */;
 	}

transport-helper.c

@@ -320,6 +320,21 @@ static void standard_options(struct transport *t)
 	if (n >= sizeof(buf))
 		die("impossibly large verbosity value");
 	set_helper_option(t, "verbosity", buf);
+
+	switch (t->family) {
+	case TRANSPORT_FAMILY_ALL:
+		/*
+		 * this is already the default,
+		 * do not break old remote helpers by setting "all" here
+		 */
+		break;
+	case TRANSPORT_FAMILY_IPV4:
+		set_helper_option(t, "family", "ipv4");
+		break;
+	case TRANSPORT_FAMILY_IPV6:
+		set_helper_option(t, "family", "ipv6");
+		break;
+	}
 }
 
 static int release_helper(struct transport *transport)

transport.c

@@ -489,6 +489,12 @@ static int connect_setup(struct transport *transport, int for_push)
 	if (data->conn)
 		return 0;
 
+	switch (transport->family) {
+	case TRANSPORT_FAMILY_ALL: break;
+	case TRANSPORT_FAMILY_IPV4: flags |= CONNECT_IPV4; break;
+	case TRANSPORT_FAMILY_IPV6: flags |= CONNECT_IPV6; break;
+	}
+
 	data->conn = git_connect(data->fd, transport->url,
 				 for_push ? data->options.receivepack :
 				 data->options.uploadpack,

transport.h

@@ -18,6 +18,12 @@ struct git_transport_options {
 	struct push_cas_option *cas;
 };
 
+enum transport_family {
+	TRANSPORT_FAMILY_ALL = 0,
+	TRANSPORT_FAMILY_IPV4,
+	TRANSPORT_FAMILY_IPV6
+};
+
 struct transport {
 	struct remote *remote;
 	const char *url;
@@ -110,6 +116,8 @@ struct transport {
 	 * actually turns out to be smart.
 	 */
 	struct git_transport_options *smart_options;
+
+	enum transport_family family;
 };
 
 #define TRANSPORT_PUSH_ALL 1