git/serve.c
Ævar Arnfjörð Bjarmason 8b8d9a2298 protocol v2: add server-side "bundle-uri" skeleton
Add a skeleton server-side implementation of a new "bundle-uri" command
to protocol v2. This will allow conforming clients to optionally seed
their initial clones or incremental fetches from URLs containing
"*.bundle" files created with "git bundle create".

This change only performs the basic boilerplate of advertising a new
protocol v2 capability. The new 'bundle-uri' capability allows a client
to request a list of bundles. Right now, the server only returns a flush
packet, which corresponds to an empty advertisement. The bundle.* config
namespace describes which key-value pairs will be communicated across
this interface in future updates.

The critical bit right now is that the new boolean
uploadPack.adverstiseBundleURIs config value signals whether or not this
capability should be advertised at all.

An earlier version of this patch [1] used a different transfer format
than the "key=value" pairs in the current implementation. The change was
made to unify the protocol v2 command with the bundle lists provided by
independent bundle servers. Further, the standard allows for the server
to advertise a URI that contains a bundle list. This allows users
automatically discovering bundle providers that are loosely associated
with the origin server, but without the origin server knowing exactly
which bundles are currently available.

[1] https://lore.kernel.org/git/RFC-patch-v2-01.13-2fc87ce092b-20220311T155841Z-avarab@gmail.com/

The very-deep headings needed to be modified to stop at level 4 due to
documentation build issues. These were not recognized in earlier builds
since the file was previously in the Documentation/technical/ directory
and was built in a different way. With its current location, the
heavily-nested details were causing build issues and they are now
replaced with a bulletted list of details.

Co-authored-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-12-25 16:24:23 +09:00

336 lines
7.9 KiB
C

#include "cache.h"
#include "repository.h"
#include "config.h"
#include "pkt-line.h"
#include "version.h"
#include "ls-refs.h"
#include "protocol-caps.h"
#include "serve.h"
#include "upload-pack.h"
#include "bundle-uri.h"
static int advertise_sid = -1;
static int client_hash_algo = GIT_HASH_SHA1;
static int always_advertise(struct repository *r,
struct strbuf *value)
{
return 1;
}
static int agent_advertise(struct repository *r,
struct strbuf *value)
{
if (value)
strbuf_addstr(value, git_user_agent_sanitized());
return 1;
}
static int object_format_advertise(struct repository *r,
struct strbuf *value)
{
if (value)
strbuf_addstr(value, r->hash_algo->name);
return 1;
}
static void object_format_receive(struct repository *r,
const char *algo_name)
{
if (!algo_name)
die("object-format capability requires an argument");
client_hash_algo = hash_algo_by_name(algo_name);
if (client_hash_algo == GIT_HASH_UNKNOWN)
die("unknown object format '%s'", algo_name);
}
static int session_id_advertise(struct repository *r, struct strbuf *value)
{
if (advertise_sid == -1 &&
git_config_get_bool("transfer.advertisesid", &advertise_sid))
advertise_sid = 0;
if (!advertise_sid)
return 0;
if (value)
strbuf_addstr(value, trace2_session_id());
return 1;
}
static void session_id_receive(struct repository *r,
const char *client_sid)
{
if (!client_sid)
client_sid = "";
trace2_data_string("transfer", NULL, "client-sid", client_sid);
}
struct protocol_capability {
/*
* The name of the capability. The server uses this name when
* advertising this capability, and the client uses this name to
* specify this capability.
*/
const char *name;
/*
* Function queried to see if a capability should be advertised.
* Optionally a value can be specified by adding it to 'value'.
* If a value is added to 'value', the server will advertise this
* capability as "<name>=<value>" instead of "<name>".
*/
int (*advertise)(struct repository *r, struct strbuf *value);
/*
* Function called when a client requests the capability as a command.
* Will be provided a struct packet_reader 'request' which it should
* use to read the command specific part of the request. Every command
* MUST read until a flush packet is seen before sending a response.
*
* This field should be NULL for capabilities which are not commands.
*/
int (*command)(struct repository *r, struct packet_reader *request);
/*
* Function called when a client requests the capability as a
* non-command. This may be NULL if the capability does nothing.
*
* For a capability of the form "foo=bar", the value string points to
* the content after the "=" (i.e., "bar"). For simple capabilities
* (just "foo"), it is NULL.
*/
void (*receive)(struct repository *r, const char *value);
};
static struct protocol_capability capabilities[] = {
{
.name = "agent",
.advertise = agent_advertise,
},
{
.name = "ls-refs",
.advertise = ls_refs_advertise,
.command = ls_refs,
},
{
.name = "fetch",
.advertise = upload_pack_advertise,
.command = upload_pack_v2,
},
{
.name = "server-option",
.advertise = always_advertise,
},
{
.name = "object-format",
.advertise = object_format_advertise,
.receive = object_format_receive,
},
{
.name = "session-id",
.advertise = session_id_advertise,
.receive = session_id_receive,
},
{
.name = "object-info",
.advertise = always_advertise,
.command = cap_object_info,
},
{
.name = "bundle-uri",
.advertise = bundle_uri_advertise,
.command = bundle_uri_command,
},
};
void protocol_v2_advertise_capabilities(void)
{
struct strbuf capability = STRBUF_INIT;
struct strbuf value = STRBUF_INIT;
int i;
/* serve by default supports v2 */
packet_write_fmt(1, "version 2\n");
for (i = 0; i < ARRAY_SIZE(capabilities); i++) {
struct protocol_capability *c = &capabilities[i];
if (c->advertise(the_repository, &value)) {
strbuf_addstr(&capability, c->name);
if (value.len) {
strbuf_addch(&capability, '=');
strbuf_addbuf(&capability, &value);
}
strbuf_addch(&capability, '\n');
packet_write(1, capability.buf, capability.len);
}
strbuf_reset(&capability);
strbuf_reset(&value);
}
packet_flush(1);
strbuf_release(&capability);
strbuf_release(&value);
}
static struct protocol_capability *get_capability(const char *key, const char **value)
{
int i;
if (!key)
return NULL;
for (i = 0; i < ARRAY_SIZE(capabilities); i++) {
struct protocol_capability *c = &capabilities[i];
const char *out;
if (!skip_prefix(key, c->name, &out))
continue;
if (!*out) {
*value = NULL;
return c;
}
if (*out++ == '=') {
*value = out;
return c;
}
}
return NULL;
}
static int receive_client_capability(const char *key)
{
const char *value;
const struct protocol_capability *c = get_capability(key, &value);
if (!c || c->command || !c->advertise(the_repository, NULL))
return 0;
if (c->receive)
c->receive(the_repository, value);
return 1;
}
static int parse_command(const char *key, struct protocol_capability **command)
{
const char *out;
if (skip_prefix(key, "command=", &out)) {
const char *value;
struct protocol_capability *cmd = get_capability(out, &value);
if (*command)
die("command '%s' requested after already requesting command '%s'",
out, (*command)->name);
if (!cmd || !cmd->advertise(the_repository, NULL) || !cmd->command || value)
die("invalid command '%s'", out);
*command = cmd;
return 1;
}
return 0;
}
enum request_state {
PROCESS_REQUEST_KEYS,
PROCESS_REQUEST_DONE,
};
static int process_request(void)
{
enum request_state state = PROCESS_REQUEST_KEYS;
struct packet_reader reader;
int seen_capability_or_command = 0;
struct protocol_capability *command = NULL;
packet_reader_init(&reader, 0, NULL, 0,
PACKET_READ_CHOMP_NEWLINE |
PACKET_READ_GENTLE_ON_EOF |
PACKET_READ_DIE_ON_ERR_PACKET);
/*
* Check to see if the client closed their end before sending another
* request. If so we can terminate the connection.
*/
if (packet_reader_peek(&reader) == PACKET_READ_EOF)
return 1;
reader.options &= ~PACKET_READ_GENTLE_ON_EOF;
while (state != PROCESS_REQUEST_DONE) {
switch (packet_reader_peek(&reader)) {
case PACKET_READ_EOF:
BUG("Should have already died when seeing EOF");
case PACKET_READ_NORMAL:
if (parse_command(reader.line, &command) ||
receive_client_capability(reader.line))
seen_capability_or_command = 1;
else
die("unknown capability '%s'", reader.line);
/* Consume the peeked line */
packet_reader_read(&reader);
break;
case PACKET_READ_FLUSH:
/*
* If no command and no keys were given then the client
* wanted to terminate the connection.
*/
if (!seen_capability_or_command)
return 1;
/*
* The flush packet isn't consume here like it is in
* the other parts of this switch statement. This is
* so that the command can read the flush packet and
* see the end of the request in the same way it would
* if command specific arguments were provided after a
* delim packet.
*/
state = PROCESS_REQUEST_DONE;
break;
case PACKET_READ_DELIM:
/* Consume the peeked line */
packet_reader_read(&reader);
state = PROCESS_REQUEST_DONE;
break;
case PACKET_READ_RESPONSE_END:
BUG("unexpected response end packet");
}
}
if (!command)
die("no command requested");
if (client_hash_algo != hash_algo_by_ptr(the_repository->hash_algo))
die("mismatched object format: server %s; client %s\n",
the_repository->hash_algo->name,
hash_algos[client_hash_algo].name);
command->command(the_repository, &reader);
return 0;
}
void protocol_v2_serve_loop(int stateless_rpc)
{
if (!stateless_rpc)
protocol_v2_advertise_capabilities();
/*
* If stateless-rpc was requested then exit after
* a single request/response exchange
*/
if (stateless_rpc) {
process_request();
} else {
for (;;)
if (process_request())
break;
}
}