[PATCH v4 0/3] git-remote-fd & git-remote-ext

[PATCH v4 0/3] git-remote-fd & git-remote-ext

[Ilari Liusvaara]

This adds two new remote helpers.

* git-remote-fd, which connects to git service on given file descriptor(s),
useful for graphical user interfaces that want to use internal ssh client.

* git-remote-ext, which connect to git service using external program. Useful
for connecting using odd one-off ssh options, to services in abstract
namespace, using unix domain sockets, using TLS, etc...

Changes from last time:
* Refactor the transfer loop quite a bit.
* Change the "format character" in remote-ext from '\' to '%'.
* Some code changes in remote-fd.
* Documentation changes for remote-fd.

Ilari Liusvaara (3):
  Add bidirectional_transfer_loop()
  git-remote-fd
  git-remote-ext

 .gitignore                       |    2 +
 Documentation/git-remote-ext.txt |  119 ++++++++++++++
 Documentation/git-remote-fd.txt  |   59 +++++++
 Makefile                         |    2 +
 builtin.h                        |    2 +
 builtin/remote-ext.c             |  243 ++++++++++++++++++++++++++++
 builtin/remote-fd.c              |   80 ++++++++++
 compat/mingw.h                   |    5 +
 git.c                            |    2 +
 transport-helper.c               |  324 ++++++++++++++++++++++++++++++++++++++
 transport.h                      |    1 +
 11 files changed, 839 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/git-remote-ext.txt
 create mode 100644 Documentation/git-remote-fd.txt
 create mode 100644 builtin/remote-ext.c
 create mode 100644 builtin/remote-fd.c

-- 
1.7.3.1.48.g63ac7.dirty

[PATCH v4 1/3] Add bidirectional_transfer_loop()

[Ilari Liusvaara]

This helper function copies bidirectional stream of data between
stdin/stdout and specified file descriptors.

Signed-off-by: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
---
 compat/mingw.h     |    5 +
 transport-helper.c |  324 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 transport.h        |    1 +
 3 files changed, 330 insertions(+), 0 deletions(-)

diff --git a/compat/mingw.h b/compat/mingw.h
index 3b2477b..f27a7b6 100644
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -23,6 +23,9 @@ typedef int pid_t;
 #define WEXITSTATUS(x) ((x) & 0xff)
 #define WTERMSIG(x) SIGTERM
 
+#define EWOULDBLOCK EAGAIN
+#define SHUT_WR SD_SEND
+
 #define SIGHUP 1
 #define SIGQUIT 3
 #define SIGKILL 9
@@ -50,6 +53,8 @@ struct pollfd {
 };
 #define POLLIN 1
 #define POLLHUP 2
+#define POLLOUT 4
+#define POLLNVAL 8
 #endif
 
 typedef void (__cdecl *sig_handler_t)(int);
diff --git a/transport-helper.c b/transport-helper.c
index acfc88e..1f7bad6 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -862,3 +862,327 @@ int transport_helper_init(struct transport *transport, const char *name)
 	transport->smart_options = &(data->transport_options);
 	return 0;
 }
+
+/*
+ * Linux pipes can buffer 65536 bytes at once (and most platforms can
+ * buffer less), so attempt reads and writes with up to that size.
+ */
+#define BUFFERSIZE 65536
+/* This should be enough to hold debugging message. */
+#define PBUFFERSIZE 8192
+
+/* Print bidirectional transfer loop debug message. */
+static void transfer_debug(const char *fmt, ...)
+{
+	va_list args;
+	char msgbuf[PBUFFERSIZE];
+	static int debug_enabled = -1;
+
+	if (debug_enabled < 0)
+		debug_enabled = getenv("GIT_TRANSLOOP_DEBUG") ? 1 : 0;
+	if (!debug_enabled)
+		return;
+
+	va_start(args, fmt);
+	vsnprintf(msgbuf, PBUFFERSIZE, fmt, args);
+	va_end(args);
+	fprintf(stderr, "Transfer loop debugging: %s\n", msgbuf);
+}
+
+/* Stream state: More data may be coming in this direction. */
+#define SSTATE_TRANSFERING 0
+/*
+ * Stream state: No more data coming in this direction, flushing rest of
+ * data.
+ */
+#define SSTATE_FLUSHING 1
+/* Stream state: Transfer in this direction finished. */
+#define SSTATE_FINISHED 2
+
+#define STATE_NEEDS_READING(state) ((state) <= SSTATE_TRANSFERING)
+#define STATE_NEEDS_WRITING(state) ((state) <= SSTATE_FLUSHING)
+#define STATE_NEEDS_CLOSING(state) ((state) == SSTATE_FLUSHING)
+
+/* Unidirectional transfer. */
+struct unidirectional_transfer
+{
+	/* Source */
+	int src;
+	/* Destination */
+	int dest;
+	/* Is destination socket? */
+	int dest_is_sock;
+	/* Transfer state (TRANSFERING/FLUSHING/FINISHED) */
+	int state;
+	/* Buffer. */
+	char buf[BUFFERSIZE];
+	/* Buffer used. */
+	size_t bufuse;
+	/* Name of source. */
+	const char *src_name;
+	/* Name of destination. */
+	const char *dest_name;
+};
+
+static int udt_can_read(struct unidirectional_transfer *t)
+{
+	return (STATE_NEEDS_READING(t->state) && t->bufuse < BUFFERSIZE);
+}
+
+static int udt_can_write(struct unidirectional_transfer *t)
+{
+	return (STATE_NEEDS_WRITING(t->state) && t->bufuse > 0);
+}
+
+static void udt_close_if_finished(struct unidirectional_transfer *t)
+{
+	if (STATE_NEEDS_CLOSING(t->state) && !t->bufuse) {
+		t->state = SSTATE_FINISHED;
+		if (t->dest_is_sock)
+			shutdown(t->dest, SHUT_WR);
+		else
+			close(t->dest);
+		transfer_debug("Closed %s.", t->dest_name);
+	}
+}
+
+static int udt_do_read(struct unidirectional_transfer *t)
+{
+	int r;
+	transfer_debug("%s is readable", t->src_name);
+	r = read(t->src, t->buf + t->bufuse, BUFFERSIZE - t->bufuse);
+	if (r < 0 && errno != EWOULDBLOCK && errno != EAGAIN &&
+		errno != EINTR) {
+		error("read(%s) failed: %s", t->src_name, strerror(errno));
+		return -1;
+	} else if (r == 0) {
+		transfer_debug("%s EOF (with %i bytes in buffer)",
+			t->src_name, t->bufuse);
+		t->state = SSTATE_FLUSHING;
+	} else if (r > 0) {
+		t->bufuse += r;
+		transfer_debug("Read %i bytes from %s (buffer now at %i)",
+			r, t->src_name, (int)t->bufuse);
+	}
+	return 0;
+}
+
+static int udt_do_write(struct unidirectional_transfer *t)
+{
+	int r;
+	transfer_debug("%s is writable", t->dest_name);
+	r = write(t->dest, t->buf, t->bufuse);
+	if (r < 0 && errno != EWOULDBLOCK && errno != EAGAIN &&
+		errno != EINTR) {
+		error("write(%s) failed: %s", t->dest_name, strerror(errno));
+		return -1;
+	} else if (r > 0) {
+		t->bufuse -= r;
+		if(t->bufuse)
+			memmove(t->buf, t->buf + r, t->bufuse);
+		transfer_debug("Wrote %i bytes to %s (buffer now at %i)",
+			r, t->dest_name, (int)t->bufuse);
+	}
+	return 0;
+}
+
+/* State of bidirectional transfer loop. */
+struct bidirectional_transfer_state
+{
+	/*
+	 * Current polls. Up to 4 because both read and write for both
+	 * directions possibly needs to poll, and all of these may occur
+	 * at once.
+	 */
+	struct pollfd polls[4];
+	/* Number of polls active. */
+	int polls_active;
+	/* Index for stdin in poll array, -1 if none. */
+	int stdin_index;
+	/* Index for stdout in poll array, -1 if none. */
+	int stdout_index;
+	/* Index for input descriptor in poll array, -1 if none. */
+	int input_index;
+	/* Index for output descrptor in poll array, -1 if none. */
+	int output_index;
+	/* Direction from program to git. */
+	struct unidirectional_transfer ptg;
+	/* Direction from git to program. */
+	struct unidirectional_transfer gtp;
+};
+
+/*
+ * Allocate individual poll array entry.
+ * polls -> The polls array. Must have at least *active + 1 entries.
+ * active -> Place for number of active polls. Value in this location is
+ * incremented.
+ * index -> Place to store index for newly allocated entry.
+ * fd -> The file descriptor to place there.
+ * name -> Name for fd to print. If NULL, no message is printed.
+ */
+static void allocate_poll_array_entry(struct pollfd* polls, int* active,
+	int* index, int fd, const char* name)
+{
+	*index = (*active)++;
+	polls[*index].fd = fd;
+	if (name)
+		transfer_debug("Adding %s to fds to wait for...", name);
+}
+
+
+/* Allocate indexes for file descriptors in poll array. */
+static void allocate_poll_indexes(struct bidirectional_transfer_state* s)
+{
+	/* Initialize fields like there was nothing waiting. */
+	s->stdin_index = -1;
+	s->stdout_index = -1;
+	s->input_index = -1;
+	s->output_index = -1;
+	s->polls_active = 0;
+
+	if (udt_can_read(&s->ptg))
+		allocate_poll_array_entry(s->polls, &s->polls_active,
+			&s->input_index, s->ptg.src, s->ptg.src_name);
+	if (udt_can_write(&s->ptg))
+		allocate_poll_array_entry(s->polls, &s->polls_active,
+			&s->stdout_index, s->ptg.dest, s->ptg.dest_name);
+	if (udt_can_read(&s->gtp))
+		allocate_poll_array_entry(s->polls, &s->polls_active,
+			&s->stdin_index, s->gtp.src, s->gtp.src_name);
+	if (udt_can_write(&s->gtp)) {
+		if (s->gtp.dest == s->ptg.src && s->input_index >= 0)
+			s->output_index = s->input_index;
+		else
+			allocate_poll_array_entry(s->polls, &s->polls_active,
+				&s->output_index, s->gtp.dest,
+				s->gtp.dest_name);
+		transfer_debug("Adding %s to fds to wait for",
+			s->gtp.dest_name);
+	}
+}
+
+/*
+ * Set specified event flags for specified poll array entry if index is
+ * valid. If msg is not null, it is printed as debug message.
+ */
+static void mark_for_wait(struct pollfd* polls, int index, int flags,
+	const char* msg)
+{
+	if (index < 0)
+		return;		/* Index not in use. */
+	polls[index].events |= flags;
+	transfer_debug("Setting fd wait flags: fd=%i, flags=%i, index=%i",
+		polls[index].fd, flags, index);
+	if (msg)
+		transfer_debug("%s", msg);
+}
+
+/*
+ * Load the parameters into poll array and related fields based on rest of
+ * fields.
+ */
+static void load_poll_params(struct bidirectional_transfer_state* s)
+{
+	int i;
+
+	allocate_poll_indexes(s);
+	for (i = 0; i < s->polls_active; i++)
+		s->polls[i].events = s->polls[i].revents = 0;
+
+	mark_for_wait(s->polls, s->stdin_index, POLLIN,
+		"Waiting for stdin to become readable");
+	mark_for_wait(s->polls, s->input_index, POLLIN,
+		"Waiting for remote input to become readable");
+	mark_for_wait(s->polls, s->stdout_index, POLLOUT,
+		"Waiting for stdout to become writable");
+	mark_for_wait(s->polls, s->output_index, POLLOUT,
+		"Waiting for remote output to become writable");
+}
+
+/* Call handler if ready. */
+static int call_handler_if(int r, struct bidirectional_transfer_state* s,
+	int index, int flagmask, const char* name,
+	int (*on_ready)(struct unidirectional_transfer *t),
+	struct unidirectional_transfer *transfer)
+{
+	if(r)
+		return r;
+	if(index < 0)
+		return 0;		/* This is not being waited. */
+	if(s->polls[index].revents & POLLNVAL) {
+		error("%s got unexpectedly closed", name);
+		return -1;
+	}
+	if(!(s->polls[index].revents & flagmask))
+		return 0;		/* No events returned. */
+	return on_ready(transfer);
+}
+
+/* Handle events occured during poll. Returns -1 on error, 0 on success. */
+static int transfer_handle_events(struct bidirectional_transfer_state* s)
+{
+	int r = 0;
+	r = call_handler_if(r, s, s->stdin_index, POLLIN | POLLHUP,
+		s->gtp.src_name, udt_do_read, &s->gtp);
+	r = call_handler_if(r, s, s->input_index, POLLIN | POLLHUP,
+		s->ptg.src_name, udt_do_read, &s->ptg);
+	r = call_handler_if(r, s, s->output_index, POLLOUT,
+		s->gtp.dest_name, udt_do_write, &s->gtp);
+	r = call_handler_if(r, s, s->stdout_index, POLLOUT,
+		s->ptg.dest_name, udt_do_write, &s->ptg);
+	udt_close_if_finished(&s->ptg);
+	udt_close_if_finished(&s->gtp);
+	return r;
+}
+
+/*
+ * Copies data from stdin to output and from input to stdout simultaneously.
+ * Additionally filtering through given filter. If filter is NULL, uses
+ * identity filter.
+ */
+int bidirectional_transfer_loop(int input, int output)
+{
+	struct bidirectional_transfer_state state;
+
+	/* Fill the state fields. */
+	state.ptg.src = input;
+	state.ptg.dest = 1;
+	state.ptg.dest_is_sock = 0;
+	state.ptg.state = SSTATE_TRANSFERING;
+	state.ptg.bufuse = 0;
+	state.ptg.src_name = "remote input";
+	state.ptg.dest_name = "stdout";
+
+	state.gtp.src = 0;
+	state.gtp.dest = output;
+	state.gtp.dest_is_sock = (input == output);
+	state.gtp.state = SSTATE_TRANSFERING;
+	state.gtp.bufuse = 0;
+	state.gtp.src_name = "stdin";
+	state.gtp.dest_name = "remote output";
+
+	while (1) {
+		int r;
+		load_poll_params(&state);
+		if (!state.polls_active) {
+			transfer_debug("Transfer done");
+			break;
+		}
+		transfer_debug("Waiting for %i file descriptors",
+			state.polls_active);
+		r = poll(state.polls, state.polls_active, -1);
+		if (r < 0) {
+			if (errno == EWOULDBLOCK || errno == EAGAIN ||
+				errno == EINTR)
+				continue;
+			error("poll failed: %s", strerror(errno));
+			return -1;
+		} else if (r == 0)
+			continue;
+
+		r = transfer_handle_events(&state);
+		if (r)
+			return r;
+	}
+	return 0;
+}
diff --git a/transport.h b/transport.h
index c59d973..e803c0e 100644
--- a/transport.h
+++ b/transport.h
@@ -154,6 +154,7 @@ int transport_connect(struct transport *transport, const char *name,
 
 /* Transport methods defined outside transport.c */
 int transport_helper_init(struct transport *transport, const char *name);
+int bidirectional_transfer_loop(int input, int output);
 
 /* common methods used by transport.c and builtin-send-pack.c */
 void transport_verify_remote_names(int nr_heads, const char **heads);
-- 
1.7.3.1.48.g63ac7.dirty

[PATCH v4 2/3] git-remote-fd

[Ilari Liusvaara]

This remote helper reflects raw smart remote transport stream back to the
calling program. This is useful for example if some UI wants to handle
ssh itself and not use hacks via GIT_SSH.

Signed-off-by: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
---
 .gitignore                      |    1 +
 Documentation/git-remote-fd.txt |   59 ++++++++++++++++++++++++++++
 Makefile                        |    1 +
 builtin.h                       |    1 +
 builtin/remote-fd.c             |   80 +++++++++++++++++++++++++++++++++++++++
 git.c                           |    1 +
 6 files changed, 143 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/git-remote-fd.txt
 create mode 100644 builtin/remote-fd.c

diff --git a/.gitignore b/.gitignore
index 20560b8..89f37f4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -112,6 +112,7 @@
 /git-remote-https
 /git-remote-ftp
 /git-remote-ftps
+/git-remote-fd
 /git-remote-testgit
 /git-repack
 /git-replace
diff --git a/Documentation/git-remote-fd.txt b/Documentation/git-remote-fd.txt
new file mode 100644
index 0000000..1c1a179
--- /dev/null
+++ b/Documentation/git-remote-fd.txt
@@ -0,0 +1,59 @@
+git-remote-fd(1)
+=================
+
+NAME
+----
+git-remote-fd - Reflect smart transport stream back to caller
+
+SYNOPSIS
+--------
+"fd::<infd>[,<outfd>][/<anything>]" (as URL)
+
+DESCRIPTION
+-----------
+This helper uses specified file descriptors to connect to remote git server.
+This is not meant for end users but for programs and scripts calling git
+fetch, push or archive.
+
+If only <infd> is given, it is assumed to be bidirectional socket connected
+to remote git server (git-upload-pack, git-receive-pack or
+git-upload-achive). If both <infd> and <outfd> are given, they are assumed
+to be pipes connected to remote git server (<infd> being the inbound pipe
+and <outfd> being the outbound pipe.
+
+It is assumed that any handshaking procedures have already been completed
+(such as sending service request for git://) before this helper is started.
+
+<anything> can be any string. It is ignored. It is meant for provoding
+information to user in the URL in case that URL is displayed in some
+context.
+
+ENVIRONMENT VARIABLES:
+----------------------
+GIT_TRANSLOOP_DEBUG::
+	If set, prints debugging information about various reads/writes.
+
+EXAMPLES:
+---------
+git fetch fd::17 master::
+	Fetch master, using file descriptor #17 to communicate with
+	git-upload-pack.
+
+git fetch fd::17/foo master::
+	Same as above.
+
+git push fd::7,8 master (as URL)::
+	Push master, using file descriptor #7 to read data from
+	git-receive-pack and file descriptor #8 to write data to
+	same service.
+
+git push fd::7,8/bar master::
+	Same as above.
+
+Documentation
+--------------
+Documentation by Ilari Liusvaara and the git list <git@vger.kernel.org>
+
+GIT
+---
+Part of the linkgit:git[1] suite
diff --git a/Makefile b/Makefile
index 8a56b9a..7da54d7 100644
--- a/Makefile
+++ b/Makefile
@@ -728,6 +728,7 @@ BUILTIN_OBJS += builtin/read-tree.o
 BUILTIN_OBJS += builtin/receive-pack.o
 BUILTIN_OBJS += builtin/reflog.o
 BUILTIN_OBJS += builtin/remote.o
+BUILTIN_OBJS += builtin/remote-fd.o
 BUILTIN_OBJS += builtin/replace.o
 BUILTIN_OBJS += builtin/rerere.o
 BUILTIN_OBJS += builtin/reset.o
diff --git a/builtin.h b/builtin.h
index f2a25a0..1a816e1 100644
--- a/builtin.h
+++ b/builtin.h
@@ -108,6 +108,7 @@ extern int cmd_read_tree(int argc, const char **argv, const char *prefix);
 extern int cmd_receive_pack(int argc, const char **argv, const char *prefix);
 extern int cmd_reflog(int argc, const char **argv, const char *prefix);
 extern int cmd_remote(int argc, const char **argv, const char *prefix);
+extern int cmd_remote_fd(int argc, const char **argv, const char *prefix);
 extern int cmd_config(int argc, const char **argv, const char *prefix);
 extern int cmd_rerere(int argc, const char **argv, const char *prefix);
 extern int cmd_reset(int argc, const char **argv, const char *prefix);
diff --git a/builtin/remote-fd.c b/builtin/remote-fd.c
new file mode 100644
index 0000000..bb7eadc
--- /dev/null
+++ b/builtin/remote-fd.c
@@ -0,0 +1,80 @@
+#include "git-compat-util.h"
+#include "transport.h"
+
+/*
+ * URL syntax:
+ *	'fd::<inoutfd>[/<anything>]'		Read/write socket pair
+ *						<inoutfd>.
+ *	'fd::<infd>,<outfd>[/<anything>]'	Read pipe <infd> and write
+ *						pipe <outfd>.
+ *	[foo] indicates 'foo' is optional. <anything> is any string.
+ *
+ * The data output to <outfd>/<inoutfd> should be passed unmolested to
+ * git-receive-pack/git-upload-pack/git-upload-archive and output of
+ * git-receive-pack/git-upload-pack/git-upload-archive should be passed
+ * unmolested to <infd>/<inoutfd>.
+ *
+ */
+
+int input_fd = -1;
+int output_fd = -1;
+
+#define MAXCOMMAND 4096
+
+static void command_loop(void)
+{
+	char buffer[MAXCOMMAND];
+
+	while (1) {
+		size_t i;
+		if (!fgets(buffer, MAXCOMMAND - 1, stdin)) {
+			if (ferror(stdin))
+				die("Input error");
+			return;
+		}
+		/* Strip end of line characters. */
+		i = strlen(buffer);
+		while (isspace(buffer[i - 1]))
+			buffer[--i] = 0;
+
+		if (!strcmp(buffer, "capabilities")) {
+			printf("*connect\n\n");
+			fflush(stdout);
+		} else if (!strncmp(buffer, "connect ", 8)) {
+			printf("\n");
+			fflush(stdout);
+			if (bidirectional_transfer_loop(input_fd,
+				output_fd))
+				die("Copying data between file descriptors failed");
+			return;
+		} else {
+			die("Bad command: %s", buffer);
+		}
+	}
+}
+
+int cmd_remote_fd(int argc, const char **argv, const char *prefix)
+{
+	char* end;
+
+	if (argc < 3)
+		die("URL missing");
+
+	input_fd = (int)strtoul(argv[2], &end, 10);
+
+	if ((end == argv[2]) || (*end != ',' && *end !='/' && *end))
+		die("Bad URL syntax");
+
+	if (*end == '/' || !*end) {
+		output_fd = input_fd;
+	} else {
+		char* end2;
+		output_fd = (int)strtoul(end + 1, &end2, 10);
+
+		if ((end2 == end + 1) || (*end2 !='/' && *end2))
+			die("Bad URL syntax");
+	}
+
+	command_loop();
+	return 0;
+}
diff --git a/git.c b/git.c
index 50a1401..b7b96b0 100644
--- a/git.c
+++ b/git.c
@@ -374,6 +374,7 @@ static void handle_internal_command(int argc, const char **argv)
 		{ "receive-pack", cmd_receive_pack },
 		{ "reflog", cmd_reflog, RUN_SETUP },
 		{ "remote", cmd_remote, RUN_SETUP },
+		{ "remote-fd", cmd_remote_fd },
 		{ "replace", cmd_replace, RUN_SETUP },
 		{ "repo-config", cmd_config, RUN_SETUP_GENTLY },
 		{ "rerere", cmd_rerere, RUN_SETUP },
-- 
1.7.3.1.48.g63ac7.dirty

[PATCH v4 3/3] git-remote-ext

[Ilari Liusvaara]

This remote helper invokes external command and passes raw smart transport
stream through it. This is useful for instance for invoking ssh with
one-off odd options, connecting to git services in unix domain
sockets, in abstract namespace, using TLS or other secure protocols,
etc...

Signed-off-by: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
---
 .gitignore                       |    1 +
 Documentation/git-remote-ext.txt |  119 +++++++++++++++++++
 Makefile                         |    1 +
 builtin.h                        |    1 +
 builtin/remote-ext.c             |  243 ++++++++++++++++++++++++++++++++++++++
 git.c                            |    1 +
 6 files changed, 366 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/git-remote-ext.txt
 create mode 100644 builtin/remote-ext.c

diff --git a/.gitignore b/.gitignore
index 89f37f4..87b833c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -113,6 +113,7 @@
 /git-remote-ftp
 /git-remote-ftps
 /git-remote-fd
+/git-remote-ext
 /git-remote-testgit
 /git-repack
 /git-replace
diff --git a/Documentation/git-remote-ext.txt b/Documentation/git-remote-ext.txt
new file mode 100644
index 0000000..748f106
--- /dev/null
+++ b/Documentation/git-remote-ext.txt
@@ -0,0 +1,119 @@
+git-remote-ext(1)
+=================
+
+NAME
+----
+git-remote-ext - Bridge smart transport to external command.
+
+SYNOPSIS
+--------
+git remote add nick "ext::<command>[ <arguments>...]"
+
+DESCRIPTION
+-----------
+This remote helper uses the specified 'program' to connect
+to a remote git server.
+
+Command and arguments are separated by unescaped space.
+
+The following sequences have a special meaning:
+
+'% '::
+	Literal space in command or argument.
+
+'%%'::
+	Literal percent sign.
+
+'%s'::
+	Replaced with name (receive-pack, upload-pack, or
+	upload-archive) of the service git wants to invoke.
+
+'%S'::
+	Replaced with long name (git-receive-pack,
+	git-upload-pack, or git-upload-archive) of the service
+	git wants to invoke.
+
+'%G<repository>' (as argument)::
+	This argument will not be passed to 'program'. Instead, it
+	will cause helper to start by sending git:// service request to
+	remote side with service field set to approiate value and
+	repository field set to <repository>. Default is not to send
+	such request.
++
+This is useful if remote side is git:// server accessed over
+some tunnel.
+
+'%V<host>' (as argument)::
+	This argument will not be passed to 'program'. Instead it sets
+	the vhost field in git:// service request. Default is not to
+	send vhost in such request (if sent).
+
+ENVIRONMENT VARIABLES:
+----------------------
+
+GIT_TRANSLOOP_DEBUG::
+	If set, prints debugging information about various reads/writes.
+
+ENVIRONMENT VARIABLES PASSED TO COMMAND:
+----------------------------------------
+
+GIT_EXT_SERVICE::
+	Set to long name (git-upload-pack, etc...) of service helper needs
+	to invoke.
+
+GIT_EXT_SERVICE_NOPREFIX::
+	Set to long name (upload-pack, etc...) of service helper needs
+	to invoke.
+
+
+EXAMPLES:
+---------
+This remote helper is transparently used by git when
+you use commands such as "git fetch <URL>", "git clone <URL>",
+, "git push <URL>" or "git remote add nick <URL>", where <URL>
+begins with `ext::`.  Examples:
+
+"ext::ssh -i /home/foo/.ssh/somekey user&#64;host.example %S 'foo/repo'"::
+	Like host.example:foo/repo, but use /home/foo/.ssh/somekey as
+	keypair and user as user on remote side. This avoids needing to
+	edit .ssh/config.
+
+"ext::socat -t3600 - ABSTRACT-CONNECT:/git-server %G/somerepo"::
+	Represents repository with path /somerepo accessable over
+	git protocol at abstract namespace address /git-server.
+
+"ext::git-server-alias foo %G/repo"::
+	Represents a repository with path /repo accessed using the
+	helper program "git-server-alias foo".  The path to the
+	repository and type of request are not passed on the command
+	line but as part of the protocol stream, as usual with git://
+	protocol.
+
+"ext::git-server-alias foo %G/repo %Vfoo"::
+	Represents a repository with path /repo accessed using the
+	helper program "git-server-alias foo".  The hostname for the
+	remote server passed in the protocol stream will be "foo"
+	(this allows multiple virtual git servers to share a
+	link-level address).
+
+"ext::git-server-alias foo %G/repo% with% spaces %Vfoo"::
+	Represents a repository with path '/repo with spaces' accessed
+	using the helper program "git-server-alias foo".  The hostname for
+	the remote server passed in the protocol stream will be "foo"
+	(this allows multiple virtual git servers to share a
+	link-level address).
+
+"ext::git-ssl foo.example /bar"::
+	Represents a repository accessed using the helper program
+	"git-ssl foo.example /bar".  The type of request can be
+	determined by the helper using environment variables (see
+	above).
+
+Documentation
+--------------
+Documentation by Ilari Liusvaara, Jonathan Nieder and the git list
+<git@vger.kernel.org>
+
+GIT
+---
+Part of the linkgit:git[1] suite
diff --git a/Makefile b/Makefile
index 7da54d7..9909ca1 100644
--- a/Makefile
+++ b/Makefile
@@ -728,6 +728,7 @@ BUILTIN_OBJS += builtin/read-tree.o
 BUILTIN_OBJS += builtin/receive-pack.o
 BUILTIN_OBJS += builtin/reflog.o
 BUILTIN_OBJS += builtin/remote.o
+BUILTIN_OBJS += builtin/remote-ext.o
 BUILTIN_OBJS += builtin/remote-fd.o
 BUILTIN_OBJS += builtin/replace.o
 BUILTIN_OBJS += builtin/rerere.o
diff --git a/builtin.h b/builtin.h
index 1a816e1..a4bba61 100644
--- a/builtin.h
+++ b/builtin.h
@@ -108,6 +108,7 @@ extern int cmd_read_tree(int argc, const char **argv, const char *prefix);
 extern int cmd_receive_pack(int argc, const char **argv, const char *prefix);
 extern int cmd_reflog(int argc, const char **argv, const char *prefix);
 extern int cmd_remote(int argc, const char **argv, const char *prefix);
+extern int cmd_remote_ext(int argc, const char **argv, const char *prefix);
 extern int cmd_remote_fd(int argc, const char **argv, const char *prefix);
 extern int cmd_config(int argc, const char **argv, const char *prefix);
 extern int cmd_rerere(int argc, const char **argv, const char *prefix);
diff --git a/builtin/remote-ext.c b/builtin/remote-ext.c
new file mode 100644
index 0000000..b2041ff
--- /dev/null
+++ b/builtin/remote-ext.c
@@ -0,0 +1,243 @@
+#include "git-compat-util.h"
+#include "transport.h"
+#include "run-command.h"
+
+/*
+ * URL syntax:
+ *	'command [arg1 [arg2 [...]]]'	Invoke command with given arguments.
+ *	Special characters:
+ *	'% ': Literal space in argument.
+ *	'%%': Literal percent sign.
+ *	'%S': Name of service (git-upload-pack/git-upload-archive/
+ *		git-receive-pack.
+ *	'%s': Same as \s, but with possible git- prefix stripped.
+ *	'%G': Only allowed as first 'character' of argument. Do not pass this
+ *		Argument to command, instead send this as name of repository
+ *		in in-line git://-style request (also activates sending this
+ *		style of request).
+ *	'%V': Only allowed as first 'character' of argument. Used in
+ *		conjunction with '%G': Do not pass this argument to command,
+ *		instead send this as vhost in git://-style request (note: does
+ *		not activate sending git:// style request).
+ */
+
+char* git_req = NULL;
+char* git_req_vhost = NULL;
+
+static char *strip_escapes(const char *str, const char *service,
+	const char **next)
+{
+	size_t rpos = 0;
+	int escape = 0;
+	char special = 0;
+	size_t pslen = 0;
+	size_t pSlen = 0;
+	size_t psoff = 0;
+	struct strbuf ret = STRBUF_INIT;
+
+	/* Calculate prefix length for \s and lengths for \s and \S */
+	if (!strncmp(service, "git-", 4))
+		psoff = 4;
+	pSlen = strlen(service);
+	pslen = pSlen - psoff;
+
+	/* Pass the service to command. */
+	setenv("GIT_EXT_SERVICE", service, 1);
+	setenv("GIT_EXT_SERVICE_NOPREFIX", service + psoff, 1);
+
+	/* Scan the length of argument. */
+	while (str[rpos] && (escape || str[rpos] != ' ')) {
+		if (escape) {
+			switch (str[rpos]) {
+			case ' ':
+			case '%':
+			case 's':
+			case 'S':
+				break;
+			case 'G':
+			case 'V':
+				special = str[rpos];
+				if (rpos == 1)
+					break;
+				/* Fall-through to error. */
+			default:
+				die("Bad remote-ext placeholder '\\%c'.",
+					str[rpos]);
+			}
+			escape = 0;
+		} else
+			escape = (str[rpos] == '%');
+		rpos++;
+	}
+	if (escape && !str[rpos])
+		die("remote-ext command has incomplete placeholder");
+	*next = str + rpos;
+	if (**next == ' ')
+		++*next;	/* Skip over space */
+
+	/*
+	 * Do the actual placeholder substitution. The string will be short
+	 * enough not to overflow integers.
+	 */
+	rpos = special ? 2 : 0;		/* Skip first 2 bytes in specials. */
+	escape = 0;
+	while (str[rpos] && (escape || str[rpos] != ' ')) {
+		if (escape) {
+			switch(str[rpos]) {
+			case ' ':
+			case '%':
+				strbuf_addch(&ret, str[rpos]);
+				break;
+			case 's':
+				strbuf_addstr(&ret, service + psoff);
+				break;
+			case 'S':
+				strbuf_addstr(&ret, service);
+				break;
+			}
+			escape = 0;
+		} else
+			switch(str[rpos]) {
+			case '%':
+				escape = 1;
+				break;
+			default:
+				strbuf_addch(&ret, str[rpos]);
+				break;
+			}
+		rpos++;
+	}
+	switch(special) {
+	case 'G':
+		git_req = strbuf_detach(&ret, NULL);
+		return NULL;
+	case 'V':
+		git_req_vhost = strbuf_detach(&ret, NULL);
+		return NULL;
+	default:
+		return strbuf_detach(&ret, NULL);
+	}
+}
+
+/* Should be enough... */
+#define MAXARGUMENTS 256
+
+static const char **parse_argv(const char *arg, const char *service)
+{
+	int arguments = 0;
+	int i;
+	char** ret;
+	char *(temparray[MAXARGUMENTS + 1]);
+
+	while (*arg) {
+		char* ret;
+		if (arguments == MAXARGUMENTS)
+			die("remote-ext command has too many arguments");
+		ret = strip_escapes(arg, service, &arg);
+		if (ret)
+			temparray[arguments++] = ret;
+	}
+
+	ret = xcalloc(arguments + 1, sizeof(char*));
+	for (i = 0; i < arguments; i++)
+		ret[i] = temparray[i];
+
+	return (const char**)ret;
+}
+
+static void send_git_request(int stdin_fd, const char *serv, const char *repo,
+	const char *vhost)
+{
+	size_t bufferspace;
+	size_t wpos = 0;
+	char* buffer;
+
+	/*
+	 * Request needs 12 bytes extra if there is vhost (xxxx \0host=\0) and
+	 * 6 bytes extra (xxxx \0) if there is no vhost.
+	 */
+	if (vhost)
+		bufferspace = strlen(serv) + strlen(repo) + strlen(vhost) + 12;
+	else
+		bufferspace = strlen(serv) + strlen(repo) + 6;
+
+	if (bufferspace > 0xFFFF)
+		die("Request too large to send");
+	buffer = xmalloc(bufferspace);
+
+	/* Make the packet. */
+	wpos = sprintf(buffer, "%04x%s %s%c", (unsigned)bufferspace,
+		serv, repo, 0);
+
+	/* Add vhost if any. */
+	if (vhost)
+		sprintf(buffer + wpos, "host=%s%c", vhost, 0);
+
+	/* Send the request */
+	if (write_in_full(stdin_fd, buffer, bufferspace) < 0)
+		die_errno("Failed to send request");
+
+	free(buffer);
+}
+
+static int run_child(const char *arg, const char *service)
+{
+	int r;
+	struct child_process child;
+
+	memset(&child, 0, sizeof(child));
+	child.in = -1;
+	child.out = -1;
+	child.err = 0;
+	child.argv = parse_argv(arg, service);
+
+	if (start_command(&child) < 0)
+		die("Can't run specified command");
+
+	if (git_req)
+		send_git_request(child.in, service, git_req, git_req_vhost);
+
+	r = bidirectional_transfer_loop(child.out, child.in);
+	if (!r)
+		r = finish_command(&child);
+	else
+		finish_command(&child);
+	return r;
+}
+
+#define MAXCOMMAND 4096
+
+static int command_loop(const char *child)
+{
+	char buffer[MAXCOMMAND];
+
+	while (1) {
+		if (!fgets(buffer, MAXCOMMAND - 1, stdin))
+			exit(0);
+		/* Strip end of line characters. */
+		while (isspace((unsigned char)buffer[strlen(buffer) - 1]))
+			buffer[strlen(buffer) - 1] = 0;
+
+		if (!strcmp(buffer, "capabilities")) {
+			printf("*connect\n\n");
+			fflush(stdout);
+		} else if (!strncmp(buffer, "connect ", 8)) {
+			printf("\n");
+			fflush(stdout);
+			return run_child(child, buffer + 8);
+		} else {
+			fprintf(stderr, "Bad command");
+			return 1;
+		}
+	}
+}
+
+int cmd_remote_ext(int argc, const char **argv, const char *prefix)
+{
+	if (argc < 3) {
+		fprintf(stderr, "Error: URL missing");
+		exit(1);
+	}
+
+	return command_loop(argv[2]);
+}
diff --git a/git.c b/git.c
index b7b96b0..e95a1ba 100644
--- a/git.c
+++ b/git.c
@@ -374,6 +374,7 @@ static void handle_internal_command(int argc, const char **argv)
 		{ "receive-pack", cmd_receive_pack },
 		{ "reflog", cmd_reflog, RUN_SETUP },
 		{ "remote", cmd_remote, RUN_SETUP },
+		{ "remote-ext", cmd_remote_ext },
 		{ "remote-fd", cmd_remote_fd },
 		{ "replace", cmd_replace, RUN_SETUP },
 		{ "repo-config", cmd_config, RUN_SETUP_GENTLY },
-- 
1.7.3.1.48.g63ac7.dirty

Re: [PATCH v4 1/3] Add bidirectional_transfer_loop()

[Jonathan Nieder]

Ilari Liusvaara wrote:

> --- a/transport-helper.c
> +++ b/transport-helper.c
> @@ -862,3 +862,327 @@ int transport_helper_init(struct transport *transport, const char *name)
[...]
> +/* Unidirectional transfer. */
> +struct unidirectional_transfer
> +{
> +	int src;
> +	int dest;
> +	int dest_is_sock;
> +	int state;
> +	char buf[BUFFERSIZE];
> +	size_t bufuse;
> +	const char *src_name;
> +	const char *dest_name;
> +};

Nice. :)

(I would have written

	int src;
	int dest
	unsigned dest_is_sock:1;
	enum unidirectional_transfer_state state;
	char buf[BUFFERSIZE];
	...

to make the types more obvious, but I think that's more of a matter of
style.)

[...]
> +/* State of bidirectional transfer loop. */
> +struct bidirectional_transfer_state
> +{
> +	struct pollfd polls[4];
> +	int polls_active;
> +	int stdin_index;
> +	int stdout_index;
> +	int input_index;
> +	int output_index;
> +	/* Direction from program to git. */
> +	struct unidirectional_transfer ptg;
> +	/* Direction from git to program. */
> +	struct unidirectional_transfer gtp;
> +};

Sensible.

> +int bidirectional_transfer_loop(int input, int output)
> +{
> +	struct bidirectional_transfer_state state;
> +
> +	/* Fill the state fields. */
> +	state.ptg.src = input;
> +	state.ptg.dest = 1;
> +	state.ptg.dest_is_sock = 0;
> +	state.ptg.state = SSTATE_TRANSFERING;
> +	state.ptg.bufuse = 0;
> +	state.ptg.src_name = "remote input";
> +	state.ptg.dest_name = "stdout";
> +
> +	state.gtp.src = 0;
> +	state.gtp.dest = output;
> +	state.gtp.dest_is_sock = (input == output);
> +	state.gtp.state = SSTATE_TRANSFERING;
> +	state.gtp.bufuse = 0;
> +	state.gtp.src_name = "stdin";
> +	state.gtp.dest_name = "remote output";
> +
> +	while (1) {
> +		int r;
> +		load_poll_params(&state);
> +		if (!state.polls_active) {
> +			transfer_debug("Transfer done");
> +			break;
> +		}
> +		transfer_debug("Waiting for %i file descriptors",
> +			state.polls_active);
> +		r = poll(state.polls, state.polls_active, -1);
> +		if (r < 0) {
> +			if (errno == EWOULDBLOCK || errno == EAGAIN ||
> +				errno == EINTR)
> +				continue;
> +			error("poll failed: %s", strerror(errno));
> +			return -1;
> +		} else if (r == 0)
> +			continue;
> +
> +		r = transfer_handle_events(&state);
> +		if (r)
> +			return r;
> +	}
> +	return 0;
> +}

Yes, that's much clearer.

Linux's scripts/checkpatch.pl would have a few things to say, but
I have no complaint myself except the density of comments (which is a
matter of taste).

Thanks!

Re: [PATCH v4 2/3] git-remote-fd

[Jonathan Nieder]

Ilari Liusvaara wrote:

> --- /dev/null
> +++ b/Documentation/git-remote-fd.txt

Much clearer.  The synopsis still does not make me happy; the synopsis
I suggested did not make me happy, either.  Some section headers still
have trailing colons but I'm not convinced that's worth the overhead
to fix.

> --- /dev/null
> +++ b/builtin/remote-fd.c

Looks good.  Probably input_fd and output_fd should be static ---
Junio, can you fix that up?  And now that the documentation makes it
clear this is only for fetch, push, and archive, I guess I am not so
worried about the interface any more.

Re: [PATCH v4 0/3] git-remote-fd & git-remote-ext

[Jonathan Nieder]

Ilari Liusvaara wrote:

> This adds two new remote helpers.

Looks good to me.  I assume you've checked it still works. :)

Re: [PATCH v4 0/3] git-remote-fd & git-remote-ext

[Ilari Liusvaara]

On Mon, Oct 04, 2010 at 06:30:43AM -0500, Jonathan Nieder wrote:
> Ilari Liusvaara wrote:
> 
> > This adds two new remote helpers.
> 
> Looks good to me.  I assume you've checked it still works. :)

Yeah, it does:

[Ilari@<...>:~/repositories/git(remote-fd)]$ git push -f hostmirror remote-fd 
Counting objects: 27, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (20/20), done.
Writing objects: 100% (20/20), 6.80 KiB, done.
Total 20 (delta 14), reused 0 (delta 0)
To ext::socat - ABSTRACT-CONNECT:/tmp/gits %G/Ilari/git-mirror
 + 63ac78b...ae35921 remote-fd -> remote-fd (forced update)

[Ilari@<...>:~/repositories/git(remote-fd)]$ git push fd::3,4 master 4>/tmp/fin 3</tmp/fout
Counting objects: 101805, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (29579/29579), done.
Writing objects: 100% (101805/101805), 24.74 MiB | 22.43 MiB/s, done.
Total 101805 (delta 74164), reused 98023 (delta 70709)
To fd::3,4
 * [new branch]      master -> master

[Ilari@<...>:~/repositories/git(remote-fd)]$ git ls-remote 'ext::git-ssl localhost Ilari/git-mirror' refs/heads/*
depth=1 <...>
verify return:1
depth=0 <...>
verify return:1
3b4609d029e2db42b5154f019facecee49196bf0        refs/heads/html
2f76919517e98bb5e979d6c8c7bbc3478a066a21        refs/heads/maint
b43f48fc1c841a29db0817c726e3d3beb17d4ba0        refs/heads/man
9855b08d35edf8a8a441f24ff7b00e220a29f261        refs/heads/master
92b87a9bab1a84261d2381e813e58577967bdc79        refs/heads/next
cfe4082cb3c8db8eb0fe2fd67221a1076d0ace9b        refs/heads/pu
ae35921b925cce12a57f237cb627b4673e7c1032        refs/heads/remote-fd
9551e394549d4526054f8b8d3e05f9bf1cd818ce        refs/heads/todo


-Ilari

Re: [PATCH v4 0/3] git-remote-fd & git-remote-ext

[yj2133011]

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Sent from the git mailing list archive at Nabble.com.

Re: [PATCH v4 3/3] git-remote-ext

[Sverre Rabbelier]

Heya,

On Mon, Oct 4, 2010 at 13:04, Ilari Liusvaara
<ilari.liusvaara@elisanet.fi> wrote:
> +EXAMPLES:
> +---------
> +This remote helper is transparently used by git when
> +you use commands such as "git fetch <URL>", "git clone <URL>",
> +, "git push <URL>" or "git remote add nick <URL>", where <URL>
> +begins with `ext::`.  Examples:

Much better! I was hesitant about this patch in earlier iterations
because I didn't understand it's purpose, but with these examples it
makes much more sense.


> +"ext::git-server-alias foo %G/repo %Vfoo"::
> +       Represents a repository with path /repo accessed using the
> +       helper program "git-server-alias foo".  The hostname for the
> +       remote server passed in the protocol stream will be "foo"
> +       (this allows multiple virtual git servers to share a
> +       link-level address).

Can you explain better what the 'git-server-alias' helper is supposed to do?

-- 
Cheers,

Sverre Rabbelier

Re: [PATCH v4 3/3] git-remote-ext

[Sverre Rabbelier]

Heya,

On Mon, Oct 4, 2010 at 20:11, Ilari Liusvaara
<ilari.liusvaara@elisanet.fi> wrote:
> Connect its stdin and stdout to git://-type server somewhere. It might
> be that the actual address of server is variable depending on network
> conditions, the connection is tunneled somehow, etc..

SGTM, can you add that to the doc somewhere?

-- 
Cheers,

Sverre Rabbelier

Re: [PATCH v4 3/3] git-remote-ext

[Ilari Liusvaara]

On Mon, Oct 04, 2010 at 06:56:24PM +0200, Sverre Rabbelier wrote:
> 
> > +"ext::git-server-alias foo %G/repo %Vfoo"::
> > +       Represents a repository with path /repo accessed using the
> > +       helper program "git-server-alias foo".  The hostname for the
> > +       remote server passed in the protocol stream will be "foo"
> > +       (this allows multiple virtual git servers to share a
> > +       link-level address).
> 
> Can you explain better what the 'git-server-alias' helper is supposed to do?

Connect its stdin and stdout to git://-type server somewhere. It might
be that the actual address of server is variable depending on network
conditions, the connection is tunneled somehow, etc..

-Ilari

Re: [PATCH v4 2/3] git-remote-fd

[Junio C Hamano]

Jonathan Nieder <jrnieder@gmail.com> writes:

> Looks good.  Probably input_fd and output_fd should be static ---
> Junio, can you fix that up?  And now that the documentation makes it
> clear this is only for fetch, push, and archive, I guess I am not so
> worried about the interface any more.

Done, unfortunately along with quite a lot of style violation fixes...