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![Masaya Suzuki](/assets/img/avatar_default.png)
In the Git pack protocol definition, an error packet may appear only in a certain context. However, servers can face a runtime error (e.g. I/O error) at an arbitrary timing. This patch changes the protocol to allow an error packet to be sent instead of any packet. Without this protocol spec change, when a server cannot process a request, there's no way to tell that to a client. Since the server cannot produce a valid response, it would be forced to cut a connection without telling why. With this protocol spec change, the server can be more gentle in this situation. An old client may see these error packets as an unexpected packet, but this is not worse than having an unexpected EOF. Following this protocol spec change, the error packet handling code is moved to pkt-line.c. Implementation wise, this implementation uses pkt-line to communicate with a subprocess. Since this is not a part of Git protocol, it's possible that a packet that is not supposed to be an error packet is mistakenly parsed as an error packet. This error packet handling is enabled only for the Git pack protocol parsing code considering this. Signed-off-by: Masaya Suzuki <masayasuzuki@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
260 lines
6.2 KiB
C
260 lines
6.2 KiB
C
#include "cache.h"
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#include "repository.h"
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#include "config.h"
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#include "pkt-line.h"
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#include "version.h"
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#include "argv-array.h"
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#include "ls-refs.h"
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#include "serve.h"
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#include "upload-pack.h"
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static int always_advertise(struct repository *r,
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struct strbuf *value)
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{
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return 1;
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}
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static int agent_advertise(struct repository *r,
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struct strbuf *value)
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{
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if (value)
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strbuf_addstr(value, git_user_agent_sanitized());
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return 1;
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}
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struct protocol_capability {
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/*
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* The name of the capability. The server uses this name when
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* advertising this capability, and the client uses this name to
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* specify this capability.
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*/
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const char *name;
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/*
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* Function queried to see if a capability should be advertised.
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* Optionally a value can be specified by adding it to 'value'.
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* If a value is added to 'value', the server will advertise this
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* capability as "<name>=<value>" instead of "<name>".
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*/
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int (*advertise)(struct repository *r, struct strbuf *value);
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/*
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* Function called when a client requests the capability as a command.
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* The function will be provided the capabilities requested via 'keys'
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* as well as a struct packet_reader 'request' which the command should
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* use to read the command specific part of the request. Every command
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* MUST read until a flush packet is seen before sending a response.
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*
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* This field should be NULL for capabilities which are not commands.
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*/
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int (*command)(struct repository *r,
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struct argv_array *keys,
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struct packet_reader *request);
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};
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static struct protocol_capability capabilities[] = {
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{ "agent", agent_advertise, NULL },
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{ "ls-refs", always_advertise, ls_refs },
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{ "fetch", upload_pack_advertise, upload_pack_v2 },
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{ "server-option", always_advertise, NULL },
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};
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static void advertise_capabilities(void)
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{
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struct strbuf capability = STRBUF_INIT;
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struct strbuf value = STRBUF_INIT;
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int i;
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for (i = 0; i < ARRAY_SIZE(capabilities); i++) {
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struct protocol_capability *c = &capabilities[i];
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if (c->advertise(the_repository, &value)) {
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strbuf_addstr(&capability, c->name);
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if (value.len) {
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strbuf_addch(&capability, '=');
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strbuf_addbuf(&capability, &value);
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}
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strbuf_addch(&capability, '\n');
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packet_write(1, capability.buf, capability.len);
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}
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strbuf_reset(&capability);
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strbuf_reset(&value);
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}
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packet_flush(1);
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strbuf_release(&capability);
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strbuf_release(&value);
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}
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static struct protocol_capability *get_capability(const char *key)
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{
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int i;
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if (!key)
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return NULL;
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for (i = 0; i < ARRAY_SIZE(capabilities); i++) {
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struct protocol_capability *c = &capabilities[i];
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const char *out;
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if (skip_prefix(key, c->name, &out) && (!*out || *out == '='))
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return c;
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}
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return NULL;
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}
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static int is_valid_capability(const char *key)
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{
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const struct protocol_capability *c = get_capability(key);
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return c && c->advertise(the_repository, NULL);
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}
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static int is_command(const char *key, struct protocol_capability **command)
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{
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const char *out;
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if (skip_prefix(key, "command=", &out)) {
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struct protocol_capability *cmd = get_capability(out);
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if (*command)
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die("command '%s' requested after already requesting command '%s'",
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out, (*command)->name);
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if (!cmd || !cmd->advertise(the_repository, NULL) || !cmd->command)
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die("invalid command '%s'", out);
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*command = cmd;
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return 1;
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}
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return 0;
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}
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int has_capability(const struct argv_array *keys, const char *capability,
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const char **value)
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{
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int i;
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for (i = 0; i < keys->argc; i++) {
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const char *out;
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if (skip_prefix(keys->argv[i], capability, &out) &&
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(!*out || *out == '=')) {
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if (value) {
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if (*out == '=')
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out++;
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*value = out;
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}
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return 1;
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}
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}
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return 0;
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}
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enum request_state {
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PROCESS_REQUEST_KEYS,
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PROCESS_REQUEST_DONE,
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};
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static int process_request(void)
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{
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enum request_state state = PROCESS_REQUEST_KEYS;
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struct packet_reader reader;
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struct argv_array keys = ARGV_ARRAY_INIT;
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struct protocol_capability *command = NULL;
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packet_reader_init(&reader, 0, NULL, 0,
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PACKET_READ_CHOMP_NEWLINE |
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PACKET_READ_GENTLE_ON_EOF |
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PACKET_READ_DIE_ON_ERR_PACKET);
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/*
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* Check to see if the client closed their end before sending another
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* request. If so we can terminate the connection.
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*/
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if (packet_reader_peek(&reader) == PACKET_READ_EOF)
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return 1;
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reader.options &= ~PACKET_READ_GENTLE_ON_EOF;
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while (state != PROCESS_REQUEST_DONE) {
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switch (packet_reader_peek(&reader)) {
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case PACKET_READ_EOF:
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BUG("Should have already died when seeing EOF");
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case PACKET_READ_NORMAL:
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/* collect request; a sequence of keys and values */
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if (is_command(reader.line, &command) ||
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is_valid_capability(reader.line))
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argv_array_push(&keys, reader.line);
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else
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die("unknown capability '%s'", reader.line);
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/* Consume the peeked line */
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packet_reader_read(&reader);
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break;
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case PACKET_READ_FLUSH:
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/*
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* If no command and no keys were given then the client
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* wanted to terminate the connection.
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*/
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if (!keys.argc)
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return 1;
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/*
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* The flush packet isn't consume here like it is in
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* the other parts of this switch statement. This is
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* so that the command can read the flush packet and
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* see the end of the request in the same way it would
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* if command specific arguments were provided after a
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* delim packet.
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*/
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state = PROCESS_REQUEST_DONE;
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break;
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case PACKET_READ_DELIM:
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/* Consume the peeked line */
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packet_reader_read(&reader);
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state = PROCESS_REQUEST_DONE;
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break;
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}
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}
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if (!command)
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die("no command requested");
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command->command(the_repository, &keys, &reader);
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argv_array_clear(&keys);
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return 0;
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}
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/* Main serve loop for protocol version 2 */
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void serve(struct serve_options *options)
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{
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if (options->advertise_capabilities || !options->stateless_rpc) {
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/* serve by default supports v2 */
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packet_write_fmt(1, "version 2\n");
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advertise_capabilities();
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/*
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* If only the list of capabilities was requested exit
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* immediately after advertising capabilities
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*/
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if (options->advertise_capabilities)
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return;
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}
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/*
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* If stateless-rpc was requested then exit after
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* a single request/response exchange
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*/
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if (options->stateless_rpc) {
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process_request();
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} else {
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for (;;)
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if (process_request())
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break;
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}
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}
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