Subject: Re: [PATCH v2 08/27] connect: discover protocol version outside of get_remote_heads

From: Brandon Williams <[email-masked]>
Date: Thu, 1 Feb 2018 09:57:05 -0800

On 01/31, Derrick Stolee wrote:
> On 1/25/2018 6:58 PM, Brandon Williams wrote:
> > In order to prepare for the addition of protocol_v2 push the protocol
> > version discovery outside of 'get_remote_heads()'.  This will allow for
> > keeping the logic for processing the reference advertisement for
> > protocol_v1 and protocol_v0 separate from the logic for protocol_v2.
> > 
> > Signed-off-by: Brandon Williams <[email-masked]>
> > ---
> >   builtin/fetch-pack.c | 16 +++++++++++++++-
> >   builtin/send-pack.c  | 17 +++++++++++++++--
> >   connect.c            | 27 ++++++++++-----------------
> >   connect.h            |  3 +++
> >   remote-curl.c        | 20 ++++++++++++++++++--
> >   remote.h             |  5 +++--
> >   transport.c          | 24 +++++++++++++++++++-----
> >   7 files changed, 83 insertions(+), 29 deletions(-)
> > 
> > diff --git a/builtin/fetch-pack.c b/builtin/fetch-pack.c
> > index 366b9d13f..85d4faf76 100644
> > --- a/builtin/fetch-pack.c
> > +++ b/builtin/fetch-pack.c
> > @@ -4,6 +4,7 @@
> >   #include "remote.h"
> >   #include "connect.h"
> >   #include "sha1-array.h"
> > +#include "protocol.h"
> >   static const char fetch_pack_usage[] =
> >   "git fetch-pack [--all] [--stdin] [--quiet | -q] [--keep | -k] [--thin] "
> > @@ -52,6 +53,7 @@ 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 packet_reader reader;
> >   	packet_trace_identity("fetch-pack");
> > @@ -193,7 +195,19 @@ 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);
> > +
> > +	packet_reader_init(&reader, fd[0], NULL, 0,
> > +			   PACKET_READ_CHOMP_NEWLINE |
> > +			   PACKET_READ_GENTLE_ON_EOF);
> > +
> > +	switch (discover_version(&reader)) {
> > +	case protocol_v1:
> > +	case protocol_v0:
> > +		get_remote_heads(&reader, &ref, 0, NULL, &shallow);
> > +		break;
> > +	case protocol_unknown_version:
> > +		BUG("unknown protocol version");
> 
> Is this really a BUG in the client, or a bug/incompatibility in the server?
> 
> Perhaps I'm misunderstanding, but it looks like discover_version() will
> die() on an unknown version (the die() is in
> protocol.c:determine_protocol_version_client()). So maybe that's why this is
> a BUG()?
> 
> If there is something to change here, this BUG() appears three more times.

Yes, I have it labeled as a BUG because discover_version can't return an
unknown protocol version.  If the server actually returns an unknown
protocol version then it should be handled in
protocol.c:determine_protocol_version_client() as you mentioned.

> 
> > +	}
> >   	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..83cb125a6 100644
> > --- a/builtin/send-pack.c
> > +++ b/builtin/send-pack.c
> > @@ -14,6 +14,7 @@
> >   #include "sha1-array.h"
> >   #include "gpg-interface.h"
> >   #include "gettext.h"
> > +#include "protocol.h"
> >   static const char * const send_pack_usage[] = {
> >   	N_("git send-pack [--all | --mirror] [--dry-run] [--force] "
> > @@ -154,6 +155,7 @@ 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 packet_reader reader;
> >   	struct option options[] = {
> >   		OPT__VERBOSITY(&verbose),
> > @@ -256,8 +258,19 @@ 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);
> > +	packet_reader_init(&reader, fd[0], NULL, 0,
> > +			   PACKET_READ_CHOMP_NEWLINE |
> > +			   PACKET_READ_GENTLE_ON_EOF);
> > +
> > +	switch (discover_version(&reader)) {
> > +	case protocol_v1:
> > +	case protocol_v0:
> > +		get_remote_heads(&reader, &remote_refs, REF_NORMAL,
> > +				 &extra_have, &shallow);
> > +		break;
> > +	case protocol_unknown_version:
> > +		BUG("unknown protocol version");
> > +	}
> >   	transport_verify_remote_names(nr_refspecs, refspecs);
> > diff --git a/connect.c b/connect.c
> > index 00e90075c..db3c9d24c 100644
> > --- a/connect.c
> > +++ b/connect.c
> > @@ -62,7 +62,7 @@ static void die_initial_contact(int unexpected)
> >   		      "and the repository exists."));
> >   }
> > -static enum protocol_version discover_version(struct packet_reader *reader)
> > +enum protocol_version discover_version(struct packet_reader *reader)
> >   {
> >   	enum protocol_version version = protocol_unknown_version;
> > @@ -234,7 +234,7 @@ enum get_remote_heads_state {
> >   /*
> >    * Read all the refs from the other end
> >    */
> > -struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
> > +struct ref **get_remote_heads(struct packet_reader *reader,
> >   			      struct ref **list, unsigned int flags,
> >   			      struct oid_array *extra_have,
> >   			      struct oid_array *shallow_points)
> > @@ -242,24 +242,17 @@ struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
> >   	struct ref **orig_list = list;
> >   	int len = 0;
> >   	enum get_remote_heads_state state = EXPECTING_FIRST_REF;
> > -	struct packet_reader reader;
> >   	const char *arg;
> > -	packet_reader_init(&reader, in, src_buf, src_len,
> > -			   PACKET_READ_CHOMP_NEWLINE |
> > -			   PACKET_READ_GENTLE_ON_EOF);
> > -
> > -	discover_version(&reader);
> > -
> >   	*list = NULL;
> >   	while (state != EXPECTING_DONE) {
> > -		switch (packet_reader_read(&reader)) {
> > +		switch (packet_reader_read(reader)) {
> >   		case PACKET_READ_EOF:
> >   			die_initial_contact(1);
> >   		case PACKET_READ_NORMAL:
> > -			len = reader.pktlen;
> > -			if (len > 4 && skip_prefix(reader.line, "ERR ", &arg))
> > +			len = reader->pktlen;
> > +			if (len > 4 && skip_prefix(reader->line, "ERR ", &arg))
> >   				die("remote error: %s", arg);
> >   			break;
> >   		case PACKET_READ_FLUSH:
> > @@ -271,22 +264,22 @@ struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
> >   		switch (state) {
> >   		case EXPECTING_FIRST_REF:
> > -			process_capabilities(reader.line, &len);
> > -			if (process_dummy_ref(reader.line)) {
> > +			process_capabilities(reader->line, &len);
> > +			if (process_dummy_ref(reader->line)) {
> >   				state = EXPECTING_SHALLOW;
> >   				break;
> >   			}
> >   			state = EXPECTING_REF;
> >   			/* fallthrough */
> >   		case EXPECTING_REF:
> > -			if (process_ref(reader.line, len, &list, flags, extra_have))
> > +			if (process_ref(reader->line, len, &list, flags, extra_have))
> >   				break;
> >   			state = EXPECTING_SHALLOW;
> >   			/* fallthrough */
> >   		case EXPECTING_SHALLOW:
> > -			if (process_shallow(reader.line, len, shallow_points))
> > +			if (process_shallow(reader->line, len, shallow_points))
> >   				break;
> > -			die("protocol error: unexpected '%s'", reader.line);
> > +			die("protocol error: unexpected '%s'", reader->line);
> >   		case EXPECTING_DONE:
> >   			break;
> >   		}
> > diff --git a/connect.h b/connect.h
> > index 01f14cdf3..cdb8979dc 100644
> > --- a/connect.h
> > +++ b/connect.h
> > @@ -13,4 +13,7 @@ extern int parse_feature_request(const char *features, const char *feature);
> >   extern const char *server_feature_value(const char *feature, int *len_ret);
> >   extern int url_is_local_not_ssh(const char *url);
> > +struct packet_reader;
> > +extern enum protocol_version discover_version(struct packet_reader *reader);
> > +
> >   #endif
> > diff --git a/remote-curl.c b/remote-curl.c
> > index 0053b0954..9f6d07683 100644
> > --- a/remote-curl.c
> > +++ b/remote-curl.c
> > @@ -1,6 +1,7 @@
> >   #include "cache.h"
> >   #include "config.h"
> >   #include "remote.h"
> > +#include "connect.h"
> >   #include "strbuf.h"
> >   #include "walker.h"
> >   #include "http.h"
> > @@ -13,6 +14,7 @@
> >   #include "credential.h"
> >   #include "sha1-array.h"
> >   #include "send-pack.h"
> > +#include "protocol.h"
> >   static struct remote *remote;
> >   /* always ends with a trailing slash */
> > @@ -176,8 +178,22 @@ static struct discovery *last_discovery;
> >   static struct ref *parse_git_refs(struct discovery *heads, int for_push)
> >   {
> >   	struct ref *list = NULL;
> > -	get_remote_heads(-1, heads->buf, heads->len, &list,
> > -			 for_push ? REF_NORMAL : 0, NULL, &heads->shallow);
> > +	struct packet_reader reader;
> > +
> > +	packet_reader_init(&reader, -1, heads->buf, heads->len,
> > +			   PACKET_READ_CHOMP_NEWLINE |
> > +			   PACKET_READ_GENTLE_ON_EOF);
> > +
> > +	switch (discover_version(&reader)) {
> > +	case protocol_v1:
> > +	case protocol_v0:
> > +		get_remote_heads(&reader, &list, for_push ? REF_NORMAL : 0,
> > +				 NULL, &heads->shallow);
> > +		break;
> > +	case protocol_unknown_version:
> > +		BUG("unknown protocol version");
> > +	}
> > +
> >   	return list;
> >   }
> > diff --git a/remote.h b/remote.h
> > index 1f6611be2..2016461df 100644
> > --- a/remote.h
> > +++ b/remote.h
> > @@ -150,10 +150,11 @@ int check_ref_type(const struct ref *ref, int flags);
> >   void free_refs(struct ref *ref);
> >   struct oid_array;
> > -extern struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
> > +struct packet_reader;
> > +extern struct ref **get_remote_heads(struct packet_reader *reader,
> >   				     struct ref **list, unsigned int flags,
> >   				     struct oid_array *extra_have,
> > -				     struct oid_array *shallow);
> > +				     struct oid_array *shallow_points);
> >   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 8e8779096..63c3dbab9 100644
> > --- a/transport.c
> > +++ b/transport.c
> > @@ -18,6 +18,7 @@
> >   #include "sha1-array.h"
> >   #include "sigchain.h"
> >   #include "transport-internal.h"
> > +#include "protocol.h"
> >   static void set_upstreams(struct transport *transport, struct ref *refs,
> >   	int pretend)
> > @@ -190,13 +191,26 @@ static int connect_setup(struct transport *transport, int for_push)
> >   static struct ref *get_refs_via_connect(struct transport *transport, int for_push)
> >   {
> >   	struct git_transport_data *data = transport->data;
> > -	struct ref *refs;
> > +	struct ref *refs = NULL;
> > +	struct packet_reader reader;
> >   	connect_setup(transport, for_push);
> > -	get_remote_heads(data->fd[0], NULL, 0, &refs,
> > -			 for_push ? REF_NORMAL : 0,
> > -			 &data->extra_have,
> > -			 &data->shallow);
> > +
> > +	packet_reader_init(&reader, data->fd[0], NULL, 0,
> > +			   PACKET_READ_CHOMP_NEWLINE |
> > +			   PACKET_READ_GENTLE_ON_EOF);
> > +
> > +	switch (discover_version(&reader)) {
> > +	case protocol_v1:
> > +	case protocol_v0:
> > +		get_remote_heads(&reader, &refs,
> > +				 for_push ? REF_NORMAL : 0,
> > +				 &data->extra_have,
> > +				 &data->shallow);
> > +		break;
> > +	case protocol_unknown_version:
> > +		BUG("unknown protocol version");
> > +	}
> >   	data->got_remote_heads = 1;
> >   	return refs;
> 

-- 
Brandon Williams