connect: in ref advertisement, shallows are last

Currently, get_remote_heads() parses the ref advertisement in one loop,
allowing refs and shallow lines to intersperse, despite this not being
allowed by the specification. Refactor get_remote_heads() to use two
loops instead, enforcing that refs come first, and then shallows.

This also makes it easier to teach get_remote_heads() to interpret other
lines in the ref advertisement, which will be done in a subsequent
patch.

As part of this change, this patch interprets capabilities only on the
first line in the ref advertisement, printing a warning message when
encountering capabilities on other lines.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/connect.c b/connect.c
index df56c0cbff4dfb1263917f6147bd7e1912418dd6..8e2e276b68ea6e31e817019b76f2604e46469f9a 100644 (file)
--- a/connect.c
+++ b/connect.c
@@ -11,6 +11,7 @@
 #include "string-list.h"
 #include "sha1-array.h"
 #include "transport.h"
+#include "strbuf.h"
 
 static char *server_capabilities;
 static const char *parse_feature_value(const char *, const char *, int *);
@@ -107,6 +108,104 @@ static void annotate_refs_with_symref_info(struct ref *ref)
        string_list_clear(&symref, 0);
 }
 
+/*
+ * Read one line of a server's ref advertisement into packet_buffer.
+ */
+static int read_remote_ref(int in, char **src_buf, size_t *src_len,
+                          int *responded)
+{
+       int len = packet_read(in, src_buf, src_len,
+                             packet_buffer, sizeof(packet_buffer),
+                             PACKET_READ_GENTLE_ON_EOF |
+                             PACKET_READ_CHOMP_NEWLINE);
+       const char *arg;
+       if (len < 0)
+               die_initial_contact(*responded);
+       if (len > 4 && skip_prefix(packet_buffer, "ERR ", &arg))
+               die("remote error: %s", arg);
+
+       *responded = 1;
+
+       return len;
+}
+
+#define EXPECTING_FIRST_REF 0
+#define EXPECTING_REF 1
+#define EXPECTING_SHALLOW 2
+
+static void process_capabilities(int *len)
+{
+       int nul_location = strlen(packet_buffer);
+       if (nul_location == *len)
+               return;
+       server_capabilities = xstrdup(packet_buffer + nul_location + 1);
+       *len = nul_location;
+}
+
+static int process_dummy_ref(void)
+{
+       struct object_id oid;
+       const char *name;
+
+       if (parse_oid_hex(packet_buffer, &oid, &name))
+               return 0;
+       if (*name != ' ')
+               return 0;
+       name++;
+
+       return !oidcmp(&null_oid, &oid) && !strcmp(name, "capabilities^{}");
+}
+
+static void check_no_capabilities(int len)
+{
+       if (strlen(packet_buffer) != len)
+               warning("Ignoring capabilities after first line '%s'",
+                       packet_buffer + strlen(packet_buffer));
+}
+
+static int process_ref(int len, struct ref ***list, unsigned int flags,
+                      struct oid_array *extra_have)
+{
+       struct object_id old_oid;
+       const char *name;
+
+       if (parse_oid_hex(packet_buffer, &old_oid, &name))
+               return 0;
+       if (*name != ' ')
+               return 0;
+       name++;
+
+       if (extra_have && !strcmp(name, ".have")) {
+               oid_array_append(extra_have, &old_oid);
+       } else if (!strcmp(name, "capabilities^{}")) {
+               die("protocol error: unexpected capabilities^{}");
+       } else if (check_ref(name, flags)) {
+               struct ref *ref = alloc_ref(name);
+               oidcpy(&ref->old_oid, &old_oid);
+               **list = ref;
+               *list = &ref->next;
+       }
+       check_no_capabilities(len);
+       return 1;
+}
+
+static int process_shallow(int len, struct oid_array *shallow_points)
+{
+       const char *arg;
+       struct object_id old_oid;
+
+       if (!skip_prefix(packet_buffer, "shallow ", &arg))
+               return 0;
+
+       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);
+       check_no_capabilities(len);
+       return 1;
+}
+
 /*
  * Read all the refs from the other end
  */
@@ -123,76 +222,34 @@ struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
         * 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;
+       int responded = 0;
+       int len;
+       int state = EXPECTING_FIRST_REF;
 
        *list = NULL;
-       for (saw_response = 0; ; saw_response = 1) {
-               struct ref *ref;
-               struct object_id old_oid;
-               char *name;
-               int len, name_len;
-               char *buffer = packet_buffer;
-               const char *arg;
-
-               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)
-                       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;
+       while ((len = read_remote_ref(in, &src_buf, &src_len, &responded))) {
+               switch (state) {
+               case EXPECTING_FIRST_REF:
+                       process_capabilities(&len);
+                       if (process_dummy_ref()) {
+                               state = EXPECTING_SHALLOW;
+                               break;
+                       }
+                       state = EXPECTING_REF;
+                       /* fallthrough */
+               case EXPECTING_REF:
+                       if (process_ref(len, &list, flags, extra_have))
+                               break;
+                       state = EXPECTING_SHALLOW;
+                       /* fallthrough */
+               case EXPECTING_SHALLOW:
+                       if (process_shallow(len, shallow_points))
+                               break;
+                       die("protocol error: unexpected '%s'", packet_buffer);
+               default:
+                       die("unexpected state %d", state);
                }
-
-               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);