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[RFC 6/7] transport: teach client to recognize v2 server response

From
BWBrandon Williams <bmwill@google.com>
Date
Aug 24, 2017, 22:53 UTC
Message-ID
<20170824225328.8174-7-bmwill@google.com>
In-Reply-To
<20170824225328.8174-1-bmwill@google.com>

Teach a client to recognize that a server understand protocol v2 by looking at the first pkt-line the server sends in response. This is done by looking for the response "version 2" sent by upload-pack.

Signed-off-by: Brandon Williams <bmwill@google.com>
---
 builtin/fetch-pack.c |   4 +-
 builtin/send-pack.c  |   5 +-
 connect.c            | 165 ++++++++++++++++++++++++++++++---------------------
 remote-curl.c        |   7 ++-
 remote.h             |  22 ++++++-
 transport.c          |  60 ++++++++++++++++---
 6 files changed, 178 insertions(+), 85 deletions(-)
diff --git a/builtin/fetch-pack.c b/builtin/fetch-pack.c
index 366b9d13f..a2a5e1c73 100644
--- a/builtin/fetch-pack.c
+++ b/builtin/fetch-pack.c
@@ -52,6 +52,7 @@ int cmd_fetch_pack(int argc, const char **argv, const char *prefix)
 	struct fetch_pack_args args;
 	struct oid_array shallow = OID_ARRAY_INIT;
 	struct string_list deepen_not = STRING_LIST_INIT_DUP;
+	struct remote_refs_scanner scanner;
 
 	packet_trace_identity("fetch-pack");
 
@@ -193,7 +194,8 @@ int cmd_fetch_pack(int argc, const char **argv, const char *prefix)
 		if (!conn)
 			return args.diag_url ? 0 : 1;
 	}
-	get_remote_heads(fd[0], NULL, 0, &ref, 0, NULL, &shallow);
+	remote_refs_scanner_init(&scanner, &ref, 0, NULL, &shallow);
+	get_remote_heads(fd[0], NULL, 0, &scanner);
 
 	ref = fetch_pack(&args, fd, conn, ref, dest, sought, nr_sought,
 			 &shallow, pack_lockfile_ptr);
diff --git a/builtin/send-pack.c b/builtin/send-pack.c
index fc4f0bb5f..92ec1f871 100644
--- a/builtin/send-pack.c
+++ b/builtin/send-pack.c
@@ -154,6 +154,7 @@ int cmd_send_pack(int argc, const char **argv, const char *prefix)
 	int progress = -1;
 	int from_stdin = 0;
 	struct push_cas_option cas = {0};
+	struct remote_refs_scanner scanner;
 
 	struct option options[] = {
 		OPT__VERBOSITY(&verbose),
@@ -256,8 +257,8 @@ int cmd_send_pack(int argc, const char **argv, const char *prefix)
 			args.verbose ? CONNECT_VERBOSE : 0);
 	}
 
-	get_remote_heads(fd[0], NULL, 0, &remote_refs, REF_NORMAL,
-			 &extra_have, &shallow);
+	remote_refs_scanner_init(&scanner, &remote_refs, REF_NORMAL, &extra_have, &shallow);
+	get_remote_heads(fd[0], NULL, 0, &scanner);
 
 	transport_verify_remote_names(nr_refspecs, refspecs);
 
diff --git a/connect.c b/connect.c
index d609267be..732b651d9 100644
--- a/connect.c
+++ b/connect.c
@@ -107,97 +107,124 @@ static void annotate_refs_with_symref_info(struct ref *ref)
 	string_list_clear(&symref, 0);
 }
 
-/*
- * Read all the refs from the other end
- */
-struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
+void remote_refs_scanner_init(struct remote_refs_scanner *scanner,
 			      struct ref **list, unsigned int flags,
 			      struct oid_array *extra_have,
 			      struct oid_array *shallow_points)
 {
-	struct ref **orig_list = list;
+	memset(scanner, 0, sizeof(*scanner));
+
+	scanner->orig_list = list;
+	*list = NULL;
+	scanner->list = list;
+	scanner->flags = flags;
+	scanner->extra_have = extra_have;
+	scanner->shallow_points = shallow_points;
+}
+
+int process_ref(struct remote_refs_scanner *scanner,
+		const char *buffer, int len)
+{
+	struct ref *ref;
+	struct object_id old_oid;
+	const char *name;
+	int name_len;
+	const char *arg;
+	int ret = 1;
+
+	if (len < 0)
+		die_initial_contact(scanner->seen_response);
+
+	if (!len) {
+		ret = 0;
+		goto out;
+	}
+
+	if (len > 4 && skip_prefix(buffer, "ERR ", &arg))
+		die("remote error: %s", arg);
+
+	if (len == GIT_SHA1_HEXSZ + strlen("shallow ") &&
+	    skip_prefix(buffer, "shallow ", &arg)) {
+		if (get_oid_hex(arg, &old_oid))
+			die("protocol error: expected shallow sha-1, got '%s'", arg);
+		if (!scanner->shallow_points)
+			die("repository on the other end cannot be shallow");
+		oid_array_append(scanner->shallow_points, &old_oid);
+		goto out;
+	}
+
+	if (len < GIT_SHA1_HEXSZ + 2 || get_oid_hex(buffer, &old_oid) ||
+	    buffer[GIT_SHA1_HEXSZ] != ' ')
+		die("protocol error: expected sha/ref, got '%s'", buffer);
+	name = buffer + GIT_SHA1_HEXSZ + 1;
+
+	name_len = strlen(name);
+	if (len != name_len + GIT_SHA1_HEXSZ + 1) {
+		free(server_capabilities);
+		server_capabilities = xstrdup(name + name_len + 1);
+	}
+
+	if (scanner->extra_have && !strcmp(name, ".have")) {
+		oid_array_append(scanner->extra_have, &old_oid);
+		goto out;
+	}
+
+	if (!strcmp(name, "capabilities^{}")) {
+		if (scanner->seen_response)
+			die("protocol error: unexpected capabilities^{}");
+		if (scanner->recieved_dummy_capabilities_ref)
+			die("protocol error: multiple capabilities^{}");
+		scanner->recieved_dummy_capabilities_ref = 1;
+		ret = 1;
+		goto out;
+	}
+
+	if (!check_ref(name, scanner->flags))
+		goto out;
+
+	if (scanner->recieved_dummy_capabilities_ref)
+		die("protocol error: unexpected ref after capabilities^{}");
+
+	ref = alloc_ref(buffer + GIT_SHA1_HEXSZ + 1);
+	oidcpy(&ref->old_oid, &old_oid);
+
+	*scanner->list = ref;
+	scanner->list = &ref->next;
+
+out:
+	scanner->seen_response = 1;
+	scanner->done = !ret;
+	return ret;
+}
 
+/*
+ * Read all the refs from the other end
+ */
+struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
+			      struct remote_refs_scanner *scanner)
+{
 	/*
 	 * A hang-up after seeing some response from the other end
 	 * means that it is unexpected, as we know the other end is
 	 * willing to talk to us.  A hang-up before seeing any
 	 * response does not necessarily mean an ACL problem, though.
 	 */
-	int saw_response;
-	int got_dummy_ref_with_capabilities_declaration = 0;
-
-	*list = NULL;
-	for (saw_response = 0; ; saw_response = 1) {
-		struct ref *ref;
-		struct object_id old_oid;
-		char *name;
-		int len, name_len;
+	while (!scanner->done) {
 		char *buffer = packet_buffer;
-		const char *arg;
+		int len;
 
 		len = packet_read(in, &src_buf, &src_len,
 				  packet_buffer, sizeof(packet_buffer),
 				  PACKET_READ_GENTLE_ON_EOF |
 				  PACKET_READ_CHOMP_NEWLINE);
-		if (len < 0)
-			die_initial_contact(saw_response);
 
-		if (!len)
+		if (!process_ref(scanner, buffer, len))
 			break;
-
-		if (len > 4 && skip_prefix(buffer, "ERR ", &arg))
-			die("remote error: %s", arg);
-
-		if (len == GIT_SHA1_HEXSZ + strlen("shallow ") &&
-			skip_prefix(buffer, "shallow ", &arg)) {
-			if (get_oid_hex(arg, &old_oid))
-				die("protocol error: expected shallow sha-1, got '%s'", arg);
-			if (!shallow_points)
-				die("repository on the other end cannot be shallow");
-			oid_array_append(shallow_points, &old_oid);
-			continue;
-		}
-
-		if (len < GIT_SHA1_HEXSZ + 2 || get_oid_hex(buffer, &old_oid) ||
-			buffer[GIT_SHA1_HEXSZ] != ' ')
-			die("protocol error: expected sha/ref, got '%s'", buffer);
-		name = buffer + GIT_SHA1_HEXSZ + 1;
-
-		name_len = strlen(name);
-		if (len != name_len + GIT_SHA1_HEXSZ + 1) {
-			free(server_capabilities);
-			server_capabilities = xstrdup(name + name_len + 1);
-		}
-
-		if (extra_have && !strcmp(name, ".have")) {
-			oid_array_append(extra_have, &old_oid);
-			continue;
-		}
-
-		if (!strcmp(name, "capabilities^{}")) {
-			if (saw_response)
-				die("protocol error: unexpected capabilities^{}");
-			if (got_dummy_ref_with_capabilities_declaration)
-				die("protocol error: multiple capabilities^{}");
-			got_dummy_ref_with_capabilities_declaration = 1;
-			continue;
-		}
-
-		if (!check_ref(name, flags))
-			continue;
-
-		if (got_dummy_ref_with_capabilities_declaration)
-			die("protocol error: unexpected ref after capabilities^{}");
-
-		ref = alloc_ref(buffer + GIT_SHA1_HEXSZ + 1);
-		oidcpy(&ref->old_oid, &old_oid);
-		*list = ref;
-		list = &ref->next;
 	}
 
-	annotate_refs_with_symref_info(*orig_list);
+	annotate_refs_with_symref_info(*scanner->orig_list);
 
-	return list;
+	return scanner->list;
 }
 
 static const char *parse_feature_value(const char *feature_list, const char *feature, int *lenp)
diff --git a/remote-curl.c b/remote-curl.c
index 0053b0954..04c191493 100644
--- a/remote-curl.c
+++ b/remote-curl.c
@@ -175,9 +175,12 @@ static struct discovery *last_discovery;
 
 static struct ref *parse_git_refs(struct discovery *heads, int for_push)
 {
+	struct remote_refs_scanner scanner;
 	struct ref *list = NULL;
-	get_remote_heads(-1, heads->buf, heads->len, &list,
-			 for_push ? REF_NORMAL : 0, NULL, &heads->shallow);
+	remote_refs_scanner_init(&scanner, &list, for_push ? REF_NORMAL : 0,
+				 NULL, &heads->shallow);
+	get_remote_heads(-1, heads->buf, heads->len, &scanner);
+
 	return list;
 }
 
diff --git a/remote.h b/remote.h
index 2ecf4c8c7..3a60b8fc4 100644
--- a/remote.h
+++ b/remote.h
@@ -150,10 +150,26 @@ int check_ref_type(const struct ref *ref, int flags);
 void free_refs(struct ref *ref);
 
 struct oid_array;
+
+struct remote_refs_scanner {
+	struct ref **orig_list;
+	struct ref **list;
+	unsigned int flags;
+	struct oid_array *extra_have;
+	struct oid_array *shallow_points;
+	unsigned seen_response : 1;
+	unsigned recieved_dummy_capabilities_ref : 1;
+	unsigned done : 1;
+};
+void remote_refs_scanner_init(struct remote_refs_scanner *scanner,
+			      struct ref **list, unsigned int flags,
+			      struct oid_array *extra_have,
+			      struct oid_array *shallow_points);
+int process_ref(struct remote_refs_scanner *scanner,
+		const char *buffer, int len);
+
 extern struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
-				     struct ref **list, unsigned int flags,
-				     struct oid_array *extra_have,
-				     struct oid_array *shallow);
+				     struct remote_refs_scanner *scanner);
 
 int resolve_remote_symref(struct ref *ref, struct ref *list);
 int ref_newer(const struct object_id *new_oid, const struct object_id *old_oid);
diff --git a/transport.c b/transport.c
index d75ff0514..c05e167d6 100644
--- a/transport.c
+++ b/transport.c
@@ -187,18 +187,59 @@ static int connect_setup(struct transport *transport, int for_push)
 	return 0;
 }
 
+static int determine_version(int fd, struct strbuf *packet)
+{
+	const char *v;
+	int len;
+
+	len = strbuf_packet_read(fd, packet,
+				 PACKET_READ_GENTLE_ON_EOF |
+				 PACKET_READ_CHOMP_NEWLINE);
+	if (len < 0)
+		return -1;
+
+	if (skip_prefix(packet->buf, "version ", &v)) {
+		return 2;
+	}
+
+	return 1;
+}
+
 static struct ref *get_refs_via_connect(struct transport *transport, int for_push)
 {
 	struct git_transport_data *data = transport->data;
+	struct strbuf buf = STRBUF_INIT;
+	struct remote_refs_scanner scanner;
 	struct ref *refs;
 
+	remote_refs_scanner_init(&scanner, &refs, for_push ? REF_NORMAL : 0,
+				 &data->extra_have, &data->shallow);
+
 	connect_setup(transport, for_push);
-	get_remote_heads(data->fd[0], NULL, 0, &refs,
-			 for_push ? REF_NORMAL : 0,
-			 &data->extra_have,
-			 &data->shallow);
+
+	if (0)
+		determine_version(-1, NULL);
+	switch(determine_version(data->fd[0], &buf)) {
+	case 2:
+		/* The server understands Protocol v2 */
+		fprintf(stderr, "Server understands Protocol v2!\n");
+		break;
+	case 1:
+		/* Server is speaking Protocol v1 and sent a ref so process it */
+		process_ref(&scanner, buf.buf, buf.len);
+		break;
+	default:
+		process_ref(&scanner, NULL, -1);
+		break;
+
+	}
+
+	get_remote_heads(data->fd[0], NULL, 0, &scanner);
+
 	data->got_remote_heads = 1;
 
+	strbuf_release(&buf);
+
 	return refs;
 }
 
@@ -231,9 +272,11 @@ static int fetch_refs_via_pack(struct transport *transport,
 	args.update_shallow = data->options.update_shallow;
 
 	if (!data->got_remote_heads) {
+		struct remote_refs_scanner scanner;
 		connect_setup(transport, 0);
-		get_remote_heads(data->fd[0], NULL, 0, &refs_tmp, 0,
-				 NULL, &data->shallow);
+
+		remote_refs_scanner_init(&scanner, &refs_tmp, 0, NULL, &data->shallow);
+		get_remote_heads(data->fd[0], NULL, 0, &scanner);
 		data->got_remote_heads = 1;
 	}
 
@@ -544,10 +587,11 @@ static int git_transport_push(struct transport *transport, struct ref *remote_re
 
 	if (!data->got_remote_heads) {
 		struct ref *tmp_refs;
+		struct remote_refs_scanner scanner;
 		connect_setup(transport, 1);
 
-		get_remote_heads(data->fd[0], NULL, 0, &tmp_refs, REF_NORMAL,
-				 NULL, &data->shallow);
+		remote_refs_scanner_init(&scanner, &tmp_refs, REF_NORMAL, NULL, &data->shallow);
+		get_remote_heads(data->fd[0], NULL, 0, &scanner);
 		data->got_remote_heads = 1;
 	}
 

-- 
2.14.1.342.g6490525c54-goog
Previous: Kevin DaudtNext: Brandon Williams
Message 10 of 31 in “[RFC 0/7] transitioning to protocol v2”
  1. Brandon WilliamsAug 24, 2017
  2. 1/7 pkt-line: add packet_write functionBrandon Williams, Aug 24, 2017
  3. 2/7 pkt-line: add strbuf_packet_readBrandon Williams, Aug 24, 2017
  4. 3/7 protocol: tell server that the client understands v2Brandon Williams, Aug 24, 2017
  5. Junio C HamanoAug 25, 2017
  6. Brandon WilliamsAug 25, 2017
  7. Brandon WilliamsAug 25, 2017
  8. 5/7 http: send Git-Protocol-Version headerBrandon Williams, Aug 24, 2017
  9. Kevin DaudtAug 30, 2017
  10. 6/7 transport: teach client to recognize v2 server responseBrandon Williams, Aug 24, 2017
  11. 7/7 upload-pack: ack version 2Brandon Williams, Aug 24, 2017
  12. Bryan TurnerSep 1, 2017
  13. Brandon WilliamsSep 1, 2017
  14. 4/7 t: fix ssh tests to cope with using '-o SendEnv=GIT_PROTOCOL'Brandon Williams, Aug 24, 2017
  15. Junio C HamanoAug 25, 2017
  16. Stefan BellerAug 25, 2017
  17. Junio C HamanoAug 25, 2017
  18. Jeff KingAug 25, 2017
  19. Jeff KingAug 25, 2017
  20. Jonathan NiederAug 25, 2017
  21. Jeff KingAug 25, 2017
  22. Brandon WilliamsAug 25, 2017
  23. Jeff HostetlerAug 29, 2017
  24. Brandon WilliamsAug 29, 2017
  25. Jeff KingAug 30, 2017
  26. Jeff HostetlerAug 30, 2017
  27. Brandon WilliamsAug 30, 2017
  28. Junio C HamanoAug 25, 2017
  29. Bryan TurnerAug 30, 2017
  30. Brandon WilliamsAug 30, 2017
  31. Bryan TurnerSep 1, 2017

Read the whole thread, see it on lore, or plain text.

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