upload-pack, serve: log received client session ID

When upload-pack (protocol v0/v1) or a protocol v2 server receives a
session-id capability from a client, log the received session ID via a
trace2 data event.

Signed-off-by: Josh Steadmon <steadmon@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

serve.c

@@ -201,6 +201,7 @@ static int process_request(void)
 	struct packet_reader reader;
 	struct strvec keys = STRVEC_INIT;
 	struct protocol_capability *command = NULL;
+	const char *client_sid;
 
 	packet_reader_init(&reader, 0, NULL, 0,
 			   PACKET_READ_CHOMP_NEWLINE |
@@ -264,6 +265,9 @@ static int process_request(void)
 
 	check_algorithm(the_repository, &keys);
 
+	if (has_capability(&keys, "session-id", &client_sid))
+		trace2_data_string("transfer", NULL, "client-sid", client_sid);
+
 	command->command(the_repository, &keys, &reader);
 
 	strvec_clear(&keys);

t/t5705-session-id-in-capabilities.sh

@@ -17,11 +17,14 @@ test_expect_success 'setup repos for session ID capability tests' '
 for PROTO in 0 1 2
 do
 	test_expect_success "session IDs not advertised by default (fetch v${PROTO})" '
-		test_when_finished "rm -rf local tr2-client-events" &&
+		test_when_finished "rm -rf local tr2-client-events tr2-server-events" &&
 		cp -r "$LOCAL_PRISTINE" local &&
 		GIT_TRACE2_EVENT="$(pwd)/tr2-client-events" \
-		git -c protocol.version=$PROTO -C local fetch origin &&
-		test -z "$(grep \"key\":\"server-sid\" tr2-client-events)"
+		git -c protocol.version=$PROTO -C local fetch \
+			--upload-pack "GIT_TRACE2_EVENT=\"$(pwd)/tr2-server-events\" git-upload-pack" \
+			origin &&
+		test -z "$(grep \"key\":\"server-sid\" tr2-client-events)" &&
+		test -z "$(grep \"key\":\"client-sid\" tr2-server-events)"
 	'
 
 	test_expect_success "session IDs not advertised by default (push v${PROTO})" '
@@ -43,11 +46,14 @@ test_expect_success 'enable SID advertisement' '
 for PROTO in 0 1 2
 do
 	test_expect_success "session IDs advertised (fetch v${PROTO})" '
-		test_when_finished "rm -rf local tr2-client-events" &&
+		test_when_finished "rm -rf local tr2-client-events tr2-server-events" &&
 		cp -r "$LOCAL_PRISTINE" local &&
 		GIT_TRACE2_EVENT="$(pwd)/tr2-client-events" \
-		git -c protocol.version=$PROTO -C local fetch origin &&
-		grep \"key\":\"server-sid\" tr2-client-events
+		git -c protocol.version=$PROTO -C local fetch \
+			--upload-pack "GIT_TRACE2_EVENT=\"$(pwd)/tr2-server-events\" git-upload-pack" \
+			origin &&
+		grep \"key\":\"server-sid\" tr2-client-events &&
+		grep \"key\":\"client-sid\" tr2-server-events
 	'
 
 	test_expect_success "session IDs advertised (push v${PROTO})" '

upload-pack.c

@@ -1058,6 +1058,7 @@ static void receive_needs(struct upload_pack_data *data,
 		const char *features;
 		struct object_id oid_buf;
 		const char *arg;
+		int feature_len;
 
 		reset_timeout(data->timeout);
 		if (packet_reader_read(reader) != PACKET_READ_NORMAL)
@@ -1110,6 +1111,13 @@ static void receive_needs(struct upload_pack_data *data,
 		    parse_feature_request(features, "filter"))
 			data->filter_capability_requested = 1;
 
+		arg = parse_feature_value(features, "session-id", &feature_len, NULL);
+		if (arg) {
+			char *client_sid = xstrndup(arg, feature_len);
+			trace2_data_string("transfer", NULL, "client-sid", client_sid);
+			free(client_sid);
+		}
+
 		o = parse_object(the_repository, &oid_buf);
 		if (!o) {
 			packet_writer_error(&data->writer,