amduatd: add opt-in federation config, space scoping, and tests

CMakeLists.txt

@@ -26,7 +26,8 @@ target_link_libraries(amduat_federation
 
 set(amduatd_sources src/amduatd.c src/amduatd_http.c src/amduatd_caps.c
                     src/amduatd_space.c src/amduatd_concepts.c
-                    src/amduatd_store.c src/amduatd_derivation_index.c)
+                    src/amduatd_store.c src/amduatd_derivation_index.c
+                    src/amduatd_fed.c)
 if(AMDUATD_ENABLE_UI)
   list(APPEND amduatd_sources src/amduatd_ui.c)
 endif()
@@ -117,3 +118,21 @@ target_link_libraries(amduatd_test_derivation_index
 )
 
 add_test(NAME amduatd_derivation_index COMMAND amduatd_test_derivation_index)
+
+add_executable(amduatd_test_fed_cfg
+  tests/test_amduatd_fed_cfg.c
+  src/amduatd_fed.c
+  src/amduatd_space.c
+)
+
+target_include_directories(amduatd_test_fed_cfg
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/src
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/vendor/amduat/include
+)
+
+target_link_libraries(amduatd_test_fed_cfg
+  PRIVATE amduat_asl amduat_enc amduat_util amduat_asl_pointer_fs
+)
+
+add_test(NAME amduatd_fed_cfg COMMAND amduatd_test_fed_cfg)

README.md

@@ -47,6 +47,30 @@ Run the daemon with the index-backed store:
 
 Note: `/v1/fed/records` requires the index backend.
 
+## Federation (dev)
+
+Federation is opt-in and disabled by default. Enabling federation requires the
+index-backed store and explicit flags:
+
+```sh
+./build/amduatd --root .amduat-asl --sock amduatd.sock --store-backend index \
+  --fed-enable --fed-transport unix --fed-unix-sock peer.sock \
+  --fed-domain-id 1 --fed-registry-ref <registry_ref_hex>
+```
+
+Flags:
+
+- `--fed-enable` turns on the coordinator tick loop.
+- `--fed-transport stub|unix` selects transport (`stub` by default).
+- `--fed-unix-sock PATH` configures the unix transport socket path.
+- `--fed-domain-id ID` sets the local domain id.
+- `--fed-registry-ref REF` seeds the registry reference (hex ref).
+- `--fed-require-space` rejects `/v1/fed/*` requests that do not resolve a space.
+
+`X-Amduat-Space` is honored for `/v1/fed/*` requests the same way as other
+endpoints. If `--space` is configured, unix transport requests will include the
+same `X-Amduat-Space` header when contacting peers.
+
 Run the daemon with derivation indexing enabled:
 
 ```sh

federation/transport_unix.c

@@ -687,7 +687,9 @@ static int amduat_fed_transport_unix_get_records(void *ctx,
                                                  amduat_fed_record_t **out_records,
                                                  size_t *out_len) {
   amduat_fed_transport_unix_t *transport = (amduat_fed_transport_unix_t *)ctx;
-  char req[512];
+  char req[2048];
+  char space_header[AMDUAT_ASL_POINTER_NAME_MAX + 32u];
+  const char *space_line = "";
   int fd;
   uint8_t *buf = NULL;
   size_t buf_len = 0;
@@ -703,13 +705,23 @@ static int amduat_fed_transport_unix_get_records(void *ctx,
   *out_records = NULL;
   *out_len = 0;
 
+  if (transport->has_space) {
+    snprintf(space_header,
+             sizeof(space_header),
+             "X-Amduat-Space: %s\r\n",
+             transport->space_id);
+    space_line = space_header;
+  }
+
   snprintf(req, sizeof(req),
            "GET /v1/fed/records?domain_id=%u&from_logseq=%llu HTTP/1.1\r\n"
            "Host: localhost\r\n"
+           "%s"
            "Connection: close\r\n"
            "\r\n",
            (unsigned int)domain_id,
-           (unsigned long long)from_logseq);
+           (unsigned long long)from_logseq,
+           space_line);
 
   fd = amduat_fed_transport_unix_connect(transport->socket_path);
   if (fd < 0) {
@@ -767,7 +779,9 @@ static int amduat_fed_transport_unix_get_artifact(void *ctx,
                                                   amduat_octets_t *out_bytes) {
   amduat_fed_transport_unix_t *transport = (amduat_fed_transport_unix_t *)ctx;
   char *ref_hex = NULL;
-  char req[512];
+  char req[2048];
+  char space_header[AMDUAT_ASL_POINTER_NAME_MAX + 32u];
+  const char *space_line = "";
   int fd;
   uint8_t *buf = NULL;
   size_t buf_len = 0;
@@ -783,12 +797,21 @@ static int amduat_fed_transport_unix_get_artifact(void *ctx,
   if (!amduat_asl_ref_encode_hex(ref, &ref_hex)) {
     return -1;
   }
+  if (transport->has_space) {
+    snprintf(space_header,
+             sizeof(space_header),
+             "X-Amduat-Space: %s\r\n",
+             transport->space_id);
+    space_line = space_header;
+  }
   snprintf(req, sizeof(req),
            "GET /v1/fed/artifacts/%s HTTP/1.1\r\n"
            "Host: localhost\r\n"
+           "%s"
            "Connection: close\r\n"
            "\r\n",
-           ref_hex);
+           ref_hex,
+           space_line);
   free(ref_hex);
 
   fd = amduat_fed_transport_unix_connect(transport->socket_path);
@@ -837,6 +860,34 @@ bool amduat_fed_transport_unix_init(amduat_fed_transport_unix_t *transport,
   memset(transport->socket_path, 0, sizeof(transport->socket_path));
   strncpy(transport->socket_path, socket_path,
           AMDUAT_FED_TRANSPORT_UNIX_PATH_MAX - 1u);
+  memset(transport->space_id, 0, sizeof(transport->space_id));
+  transport->has_space = false;
+  return true;
+}
+
+bool amduat_fed_transport_unix_set_space(amduat_fed_transport_unix_t *transport,
+                                         const char *space_id) {
+  size_t len;
+  size_t i;
+  if (transport == NULL) {
+    return false;
+  }
+  memset(transport->space_id, 0, sizeof(transport->space_id));
+  transport->has_space = false;
+  if (space_id == NULL || space_id[0] == '\0') {
+    return true;
+  }
+  len = strlen(space_id);
+  if (len >= sizeof(transport->space_id)) {
+    return false;
+  }
+  for (i = 0; i < len; ++i) {
+    if (space_id[i] == '\r' || space_id[i] == '\n') {
+      return false;
+    }
+  }
+  memcpy(transport->space_id, space_id, len);
+  transport->has_space = true;
   return true;
 }
 

federation/transport_unix.h

@@ -2,6 +2,7 @@
 #define AMDUAT_FED_TRANSPORT_UNIX_H
 
 #include "federation/coord.h"
+#include "amduat/asl/asl_pointer_fs.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -11,11 +12,16 @@ enum { AMDUAT_FED_TRANSPORT_UNIX_PATH_MAX = 1024 };
 
 typedef struct {
   char socket_path[AMDUAT_FED_TRANSPORT_UNIX_PATH_MAX];
+  char space_id[AMDUAT_ASL_POINTER_NAME_MAX + 1u];
+  bool has_space;
 } amduat_fed_transport_unix_t;
 
 bool amduat_fed_transport_unix_init(amduat_fed_transport_unix_t *transport,
                                     const char *socket_path);
 
+bool amduat_fed_transport_unix_set_space(amduat_fed_transport_unix_t *transport,
+                                         const char *space_id);
+
 amduat_fed_transport_t amduat_fed_transport_unix_ops(
     amduat_fed_transport_unix_t *transport);
 

src/amduatd.c

@@ -26,6 +26,7 @@
 #include "amduat/tgk/core.h"
 #include "federation/coord.h"
 #include "federation/transport_stub.h"
+#include "federation/transport_unix.h"
 #include "amduat/pel/program_dag.h"
 #include "amduat/pel/program_dag_desc.h"
 #include "amduat/pel/opreg_kernel.h"
@@ -38,6 +39,7 @@
 #include "amduatd_ui.h"
 #include "amduatd_caps.h"
 #include "amduatd_space.h"
+#include "amduatd_fed.h"
 #include "amduatd_store.h"
 #include "amduatd_derivation_index.h"
 
@@ -975,8 +977,37 @@ static bool amduatd_parse_u32_str(const char *s, uint32_t *out) {
   return true;
 }
 
+static bool amduatd_fed_require_space(int fd,
+                                      const amduatd_fed_cfg_t *fed_cfg,
+                                      const amduatd_http_req_t *req) {
+  amduat_octets_t scoped = amduat_octets(NULL, 0u);
+  const char *err = NULL;
+  char msg[128];
+
+  if (fed_cfg == NULL || req == NULL) {
+    return amduatd_http_send_text(fd, 500, "Internal Server Error",
+                                 "internal error\n", false);
+  }
+  if (!amduatd_fed_scope_names(fed_cfg,
+                               req->effective_space,
+                               "fed",
+                               &scoped,
+                               &err)) {
+    const char *reason = err != NULL ? err : "invalid X-Amduat-Space";
+    int n = snprintf(msg, sizeof(msg), "%s\n", reason);
+    if (n <= 0 || (size_t)n >= sizeof(msg)) {
+      return amduatd_http_send_text(fd, 400, "Bad Request",
+                                   "invalid X-Amduat-Space\n", false);
+    }
+    return amduatd_http_send_text(fd, 400, "Bad Request", msg, false);
+  }
+  amduat_octets_free(&scoped);
+  return true;
+}
+
 static bool amduatd_handle_get_fed_records(int fd,
                                            amduat_asl_store_t *store,
+                                           const amduatd_fed_cfg_t *fed_cfg,
                                            const amduatd_http_req_t *req) {
   char domain_buf[32];
   char from_buf[32];
@@ -997,6 +1028,9 @@ static bool amduatd_handle_get_fed_records(int fd,
     return amduatd_http_send_text(fd, 500, "Internal Server Error",
                                  "internal error\n", false);
   }
+  if (!amduatd_fed_require_space(fd, fed_cfg, req)) {
+    return false;
+  }
   if (amduatd_query_param(req->path, "domain_id",
                           domain_buf, sizeof(domain_buf)) == NULL ||
       !amduatd_parse_u32_str(domain_buf, &domain_id)) {
@@ -1179,6 +1213,7 @@ fed_records_oom:
 
 static bool amduatd_handle_get_fed_artifact(int fd,
                                             amduat_asl_store_t *store,
+                                            const amduatd_fed_cfg_t *fed_cfg,
                                             const amduatd_http_req_t *req,
                                             const char *path) {
   char no_query[1024];
@@ -1191,6 +1226,9 @@ static bool amduatd_handle_get_fed_artifact(int fd,
     return amduatd_http_send_text(fd, 500, "Internal Server Error",
                                  "internal error\n", false);
   }
+  if (!amduatd_fed_require_space(fd, fed_cfg, req)) {
+    return false;
+  }
   amduatd_path_without_query(path, no_query, sizeof(no_query));
   if (strncmp(no_query, "/v1/fed/artifacts/", 18) != 0) {
     return amduatd_http_send_text(fd, 404, "Not Found", "not found\n", false);
@@ -1228,13 +1266,20 @@ static bool amduatd_handle_get_fed_artifact(int fd,
 
 static bool amduatd_handle_get_fed_status(int fd,
                                           const amduat_fed_coord_t *coord,
+                                          const amduatd_fed_cfg_t *fed_cfg,
                                           const amduatd_http_req_t *req) {
   amduat_fed_coord_status_t status;
   char *ref_hex = NULL;
   char json[512];
   int n;
 
-  (void)req;
+  if (!amduatd_fed_require_space(fd, fed_cfg, req)) {
+    return false;
+  }
+  if (coord == NULL || fed_cfg == NULL || !fed_cfg->enabled) {
+    return amduatd_http_send_text(fd, 503, "Service Unavailable",
+                                 "federation disabled\n", false);
+  }
   amduat_fed_coord_get_status(coord, &status);
   if (status.registry_ref.hash_id != 0 &&
       status.registry_ref.digest.data != NULL) {
@@ -3870,6 +3915,7 @@ static bool amduatd_handle_conn(int fd,
                                 amduat_reference_t ui_ref,
                                 amduatd_concepts_t *concepts,
                                 const amduatd_cfg_t *dcfg,
+                                const amduatd_fed_cfg_t *fed_cfg,
                                 const amduat_fed_coord_t *coord,
                                 const amduatd_allowlist_t *allowlist,
                                 amduatd_caps_t *caps,
@@ -3971,12 +4017,12 @@ static bool amduatd_handle_conn(int fd,
   }
   if (strcmp(req.method, "GET") == 0 &&
       strcmp(no_query, "/v1/fed/records") == 0) {
-    ok = amduatd_handle_get_fed_records(fd, store, &req);
+    ok = amduatd_handle_get_fed_records(fd, store, fed_cfg, &req);
     goto conn_cleanup;
   }
   if (strcmp(req.method, "GET") == 0 &&
       strcmp(no_query, "/v1/fed/status") == 0) {
-    ok = amduatd_handle_get_fed_status(fd, coord, &req);
+    ok = amduatd_handle_get_fed_status(fd, coord, fed_cfg, &req);
     goto conn_cleanup;
   }
 
@@ -4042,7 +4088,7 @@ static bool amduatd_handle_conn(int fd,
   }
   if (strcmp(req.method, "GET") == 0 &&
       strncmp(no_query, "/v1/fed/artifacts/", 18) == 0) {
-    ok = amduatd_handle_get_fed_artifact(fd, store, &req, req.path);
+    ok = amduatd_handle_get_fed_artifact(fd, store, fed_cfg, &req, req.path);
     goto conn_cleanup;
   }
   if (strcmp(req.method, "GET") == 0 &&
@@ -4089,6 +4135,10 @@ static void amduatd_print_usage(FILE *stream) {
           "         [--space SPACE_ID] [--migrate-unscoped-edges]\n"
           "         [--edges-refresh-ms MS]\n"
           "         [--store-backend fs|index]\n"
+          "         [--fed-enable] [--fed-transport stub|unix]\n"
+          "         [--fed-unix-sock PATH]\n"
+          "         [--fed-domain-id ID] [--fed-registry-ref REF]\n"
+          "         [--fed-require-space]\n"
           "         [--allow-uid UID] [--allow-user NAME]\n"
           "         [--enable-cap-reads]\n"
           "         [--enable-derivation-index]\n"
@@ -4116,14 +4166,17 @@ int main(int argc, char **argv) {
   amduat_reference_t api_contract_ref;
   amduat_reference_t ui_ref;
   amduatd_concepts_t concepts;
+  amduatd_fed_cfg_t fed_cfg;
   amduat_fed_transport_stub_t fed_stub;
-  amduat_fed_coord_cfg_t fed_cfg;
+  amduat_fed_transport_unix_t fed_unix;
+  amduat_fed_coord_cfg_t fed_coord_cfg;
   amduat_fed_coord_t *fed_coord = NULL;
   amduatd_allowlist_t allowlist;
   int i;
   int sfd = -1;
   uint64_t last_tick_ms = 0;
   uint64_t last_edges_refresh_ms = 0;
+  const char *fed_err = NULL;
 
   memset(&api_contract_ref, 0, sizeof(api_contract_ref));
   memset(&ui_ref, 0, sizeof(ui_ref));
@@ -4131,8 +4184,18 @@ int main(int argc, char **argv) {
   memset(&allowlist, 0, sizeof(allowlist));
   memset(&dcfg, 0, sizeof(dcfg));
   memset(&caps, 0, sizeof(caps));
+  amduatd_fed_cfg_init(&fed_cfg);
 
   for (i = 1; i < argc; ++i) {
+    amduatd_fed_parse_result_t fed_rc;
+    fed_rc = amduatd_fed_cfg_parse_arg(&fed_cfg, argc, argv, &i, &fed_err);
+    if (fed_rc == AMDUATD_FED_PARSE_OK) {
+      continue;
+    }
+    if (fed_rc == AMDUATD_FED_PARSE_ERROR) {
+      fprintf(stderr, "error: %s\n", fed_err != NULL ? fed_err : "fed parse error");
+      return 2;
+    }
     if (strcmp(argv[i], "--root") == 0) {
       if (i + 1 >= argc) {
         fprintf(stderr, "error: --root requires a path\n");
@@ -4231,6 +4294,13 @@ int main(int argc, char **argv) {
     return 2;
   }
 
+  if (!amduatd_fed_requirements_check(store_backend, &fed_cfg, &fed_err)) {
+    fprintf(stderr,
+            "error: %s\n",
+            fed_err != NULL ? fed_err : "invalid federation config");
+    return 2;
+  }
+
   if (!amduatd_store_init(&store, &cfg, &store_ctx, root, store_backend)) {
     fprintf(stderr, "error: failed to initialize store: %s\n", root);
     return 8;
@@ -4268,14 +4338,53 @@ int main(int argc, char **argv) {
   }
 #endif
 
+  {
+    char *registry_hex = NULL;
+    if (fed_cfg.registry_ref_set) {
+      if (!amduat_asl_ref_encode_hex(fed_cfg.registry_ref, &registry_hex)) {
+        registry_hex = NULL;
+      }
+    }
+    amduat_log(AMDUAT_LOG_INFO,
+               "federation enabled=%s transport=%s domain_id=%u registry_ref=%s require_space=%s",
+               fed_cfg.enabled ? "on" : "off",
+               amduatd_fed_transport_name(fed_cfg.transport_kind),
+               (unsigned int)fed_cfg.local_domain_id,
+               registry_hex != NULL ? registry_hex : "null",
+               fed_cfg.require_space ? "on" : "off");
+    free(registry_hex);
+  }
+
   amduat_fed_transport_stub_init(&fed_stub);
-  memset(&fed_cfg, 0, sizeof(fed_cfg));
-  fed_cfg.local_domain_id = 0;
-  fed_cfg.authoritative_store = &store;
-  fed_cfg.cache_store = NULL;
-  fed_cfg.transport = amduat_fed_transport_stub_ops(&fed_stub);
-  if (amduat_fed_coord_open(&fed_cfg, &fed_coord) != AMDUAT_FED_COORD_OK) {
-    fed_coord = NULL;
+  memset(&fed_coord_cfg, 0, sizeof(fed_coord_cfg));
+  if (fed_cfg.enabled) {
+    fed_coord_cfg.local_domain_id = fed_cfg.local_domain_id;
+    fed_coord_cfg.authoritative_store = &store;
+    fed_coord_cfg.cache_store = NULL;
+    if (fed_cfg.registry_ref_set) {
+      fed_coord_cfg.registry_ref = fed_cfg.registry_ref;
+    } else {
+      fed_coord_cfg.registry_ref = amduat_reference(0u, amduat_octets(NULL, 0u));
+    }
+    if (fed_cfg.transport_kind == AMDUATD_FED_TRANSPORT_UNIX) {
+      if (!amduat_fed_transport_unix_init(&fed_unix,
+                                          fed_cfg.unix_socket_path)) {
+        fprintf(stderr, "error: invalid --fed-unix-sock\n");
+        return 2;
+      }
+      if (dcfg.space.enabled) {
+        (void)amduat_fed_transport_unix_set_space(&fed_unix,
+                                                  dcfg.space.space_id_buf);
+      }
+      fed_coord_cfg.transport = amduat_fed_transport_unix_ops(&fed_unix);
+    } else {
+      fed_coord_cfg.transport = amduat_fed_transport_stub_ops(&fed_stub);
+    }
+    if (amduat_fed_coord_open(&fed_coord_cfg, &fed_coord) !=
+        AMDUAT_FED_COORD_OK) {
+      fprintf(stderr, "error: failed to init federation coordinator\n");
+      return 8;
+    }
   }
 
   signal(SIGINT, amduatd_on_signal);
@@ -4378,6 +4487,7 @@ int main(int argc, char **argv) {
                                 ui_ref,
                                 &concepts,
                                 &dcfg,
+                                &fed_cfg,
                                 fed_coord,
                                 &allowlist,
                                 &caps,

src/amduatd_fed.c

@@ -0,0 +1,236 @@
+#include "amduatd_fed.h"
+
+#include "amduat/asl/ref_text.h"
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+static bool amduatd_fed_parse_u32(const char *s, uint32_t *out) {
+  unsigned long val;
+  char *endp = NULL;
+  if (s == NULL || out == NULL) {
+    return false;
+  }
+  errno = 0;
+  val = strtoul(s, &endp, 10);
+  if (errno != 0 || endp == s || *endp != '\0' || val > UINT32_MAX) {
+    return false;
+  }
+  *out = (uint32_t)val;
+  return true;
+}
+
+void amduatd_fed_cfg_init(amduatd_fed_cfg_t *cfg) {
+  if (cfg == NULL) {
+    return;
+  }
+  memset(cfg, 0, sizeof(*cfg));
+  cfg->transport_kind = AMDUATD_FED_TRANSPORT_STUB;
+  cfg->registry_ref = amduat_reference(0u, amduat_octets(NULL, 0u));
+}
+
+void amduatd_fed_cfg_free(amduatd_fed_cfg_t *cfg) {
+  if (cfg == NULL) {
+    return;
+  }
+  if (cfg->registry_ref_set) {
+    amduat_reference_free(&cfg->registry_ref);
+    cfg->registry_ref_set = false;
+  }
+  amduatd_fed_cfg_init(cfg);
+}
+
+const char *amduatd_fed_transport_name(amduatd_fed_transport_kind_t kind) {
+  switch (kind) {
+    case AMDUATD_FED_TRANSPORT_STUB:
+      return "stub";
+    case AMDUATD_FED_TRANSPORT_UNIX:
+      return "unix";
+    default:
+      return "unknown";
+  }
+}
+
+amduatd_fed_parse_result_t amduatd_fed_cfg_parse_arg(amduatd_fed_cfg_t *cfg,
+                                                     int argc,
+                                                     char **argv,
+                                                     int *io_index,
+                                                     const char **out_err) {
+  const char *arg = NULL;
+  const char *value = NULL;
+
+  if (out_err != NULL) {
+    *out_err = NULL;
+  }
+  if (cfg == NULL || argv == NULL || io_index == NULL || argc <= 0) {
+    if (out_err != NULL) {
+      *out_err = "invalid fed config parse inputs";
+    }
+    return AMDUATD_FED_PARSE_ERROR;
+  }
+  if (*io_index < 0 || *io_index >= argc) {
+    if (out_err != NULL) {
+      *out_err = "fed config parse index out of range";
+    }
+    return AMDUATD_FED_PARSE_ERROR;
+  }
+
+  arg = argv[*io_index];
+  if (strcmp(arg, "--fed-enable") == 0) {
+    cfg->enabled = true;
+    return AMDUATD_FED_PARSE_OK;
+  }
+  if (strcmp(arg, "--fed-require-space") == 0) {
+    cfg->require_space = true;
+    return AMDUATD_FED_PARSE_OK;
+  }
+  if (strcmp(arg, "--fed-transport") == 0) {
+    if (*io_index + 1 >= argc) {
+      if (out_err != NULL) {
+        *out_err = "--fed-transport requires a value";
+      }
+      return AMDUATD_FED_PARSE_ERROR;
+    }
+    value = argv[++(*io_index)];
+    if (strcmp(value, "stub") == 0) {
+      cfg->transport_kind = AMDUATD_FED_TRANSPORT_STUB;
+      return AMDUATD_FED_PARSE_OK;
+    }
+    if (strcmp(value, "unix") == 0) {
+      cfg->transport_kind = AMDUATD_FED_TRANSPORT_UNIX;
+      return AMDUATD_FED_PARSE_OK;
+    }
+    if (out_err != NULL) {
+      *out_err = "invalid --fed-transport";
+    }
+    return AMDUATD_FED_PARSE_ERROR;
+  }
+  if (strcmp(arg, "--fed-unix-sock") == 0) {
+    size_t len;
+    if (*io_index + 1 >= argc) {
+      if (out_err != NULL) {
+        *out_err = "--fed-unix-sock requires a path";
+      }
+      return AMDUATD_FED_PARSE_ERROR;
+    }
+    value = argv[++(*io_index)];
+    len = strlen(value);
+    if (len == 0 || len >= sizeof(cfg->unix_socket_path)) {
+      if (out_err != NULL) {
+        *out_err = "invalid --fed-unix-sock";
+      }
+      return AMDUATD_FED_PARSE_ERROR;
+    }
+    memset(cfg->unix_socket_path, 0, sizeof(cfg->unix_socket_path));
+    memcpy(cfg->unix_socket_path, value, len);
+    cfg->unix_socket_set = true;
+    return AMDUATD_FED_PARSE_OK;
+  }
+  if (strcmp(arg, "--fed-domain-id") == 0) {
+    uint32_t domain_id = 0;
+    if (*io_index + 1 >= argc) {
+      if (out_err != NULL) {
+        *out_err = "--fed-domain-id requires a value";
+      }
+      return AMDUATD_FED_PARSE_ERROR;
+    }
+    value = argv[++(*io_index)];
+    if (!amduatd_fed_parse_u32(value, &domain_id)) {
+      if (out_err != NULL) {
+        *out_err = "invalid --fed-domain-id";
+      }
+      return AMDUATD_FED_PARSE_ERROR;
+    }
+    cfg->local_domain_id = domain_id;
+    return AMDUATD_FED_PARSE_OK;
+  }
+  if (strcmp(arg, "--fed-registry-ref") == 0) {
+    amduat_reference_t ref;
+    if (*io_index + 1 >= argc) {
+      if (out_err != NULL) {
+        *out_err = "--fed-registry-ref requires a value";
+      }
+      return AMDUATD_FED_PARSE_ERROR;
+    }
+    value = argv[++(*io_index)];
+    memset(&ref, 0, sizeof(ref));
+    if (!amduat_asl_ref_decode_hex(value, &ref)) {
+      if (out_err != NULL) {
+        *out_err = "invalid --fed-registry-ref";
+      }
+      return AMDUATD_FED_PARSE_ERROR;
+    }
+    if (cfg->registry_ref_set) {
+      amduat_reference_free(&cfg->registry_ref);
+    }
+    cfg->registry_ref = ref;
+    cfg->registry_ref_set = true;
+    return AMDUATD_FED_PARSE_OK;
+  }
+
+  return AMDUATD_FED_PARSE_NOT_HANDLED;
+}
+
+bool amduatd_fed_requirements_check(amduatd_store_backend_t backend,
+                                    const amduatd_fed_cfg_t *cfg,
+                                    const char **out_err) {
+  if (out_err != NULL) {
+    *out_err = NULL;
+  }
+  if (cfg == NULL) {
+    if (out_err != NULL) {
+      *out_err = "missing fed config";
+    }
+    return false;
+  }
+  if (!cfg->enabled) {
+    return true;
+  }
+  if (backend != AMDUATD_STORE_BACKEND_INDEX) {
+    if (out_err != NULL) {
+      *out_err = "federation requires --store-backend index";
+    }
+    return false;
+  }
+  if (cfg->transport_kind == AMDUATD_FED_TRANSPORT_UNIX &&
+      !cfg->unix_socket_set) {
+    if (out_err != NULL) {
+      *out_err = "unix transport requires --fed-unix-sock";
+    }
+    return false;
+  }
+  return true;
+}
+
+bool amduatd_fed_scope_names(const amduatd_fed_cfg_t *cfg,
+                             const amduatd_space_t *space,
+                             const char *name,
+                             amduat_octets_t *out_scoped,
+                             const char **out_err) {
+  if (out_err != NULL) {
+    *out_err = NULL;
+  }
+  if (out_scoped != NULL) {
+    *out_scoped = amduat_octets(NULL, 0u);
+  }
+  if (cfg == NULL || name == NULL || out_scoped == NULL) {
+    if (out_err != NULL) {
+      *out_err = "invalid fed scope inputs";
+    }
+    return false;
+  }
+  if (cfg->require_space && (space == NULL || !space->enabled)) {
+    if (out_err != NULL) {
+      *out_err = "missing X-Amduat-Space";
+    }
+    return false;
+  }
+  if (!amduatd_space_scope_name(space, name, out_scoped)) {
+    if (out_err != NULL) {
+      *out_err = "failed to scope name";
+    }
+    return false;
+  }
+  return true;
+}

src/amduatd_fed.h

@@ -0,0 +1,65 @@
+#ifndef AMDUATD_FED_H
+#define AMDUATD_FED_H
+
+#include "amduatd_space.h"
+#include "amduatd_store.h"
+#include "federation/transport_unix.h"
+
+#include "amduat/asl/core.h"
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef enum {
+  AMDUATD_FED_TRANSPORT_STUB = 0,
+  AMDUATD_FED_TRANSPORT_UNIX = 1
+} amduatd_fed_transport_kind_t;
+
+typedef struct {
+  bool enabled;
+  bool require_space;
+  amduatd_fed_transport_kind_t transport_kind;
+  uint32_t local_domain_id;
+  bool registry_ref_set;
+  amduat_reference_t registry_ref;
+  bool unix_socket_set;
+  char unix_socket_path[AMDUAT_FED_TRANSPORT_UNIX_PATH_MAX];
+} amduatd_fed_cfg_t;
+
+typedef enum {
+  AMDUATD_FED_PARSE_OK = 0,
+  AMDUATD_FED_PARSE_NOT_HANDLED = 1,
+  AMDUATD_FED_PARSE_ERROR = 2
+} amduatd_fed_parse_result_t;
+
+void amduatd_fed_cfg_init(amduatd_fed_cfg_t *cfg);
+
+void amduatd_fed_cfg_free(amduatd_fed_cfg_t *cfg);
+
+const char *amduatd_fed_transport_name(amduatd_fed_transport_kind_t kind);
+
+amduatd_fed_parse_result_t amduatd_fed_cfg_parse_arg(amduatd_fed_cfg_t *cfg,
+                                                     int argc,
+                                                     char **argv,
+                                                     int *io_index,
+                                                     const char **out_err);
+
+bool amduatd_fed_requirements_check(amduatd_store_backend_t backend,
+                                    const amduatd_fed_cfg_t *cfg,
+                                    const char **out_err);
+
+bool amduatd_fed_scope_names(const amduatd_fed_cfg_t *cfg,
+                             const amduatd_space_t *space,
+                             const char *name,
+                             amduat_octets_t *out_scoped,
+                             const char **out_err);
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif /* AMDUATD_FED_H */

tests/test_amduatd_fed_cfg.c

@@ -0,0 +1,121 @@
+#include "amduatd_fed.h"
+
+#include "amduat/asl/ref_text.h"
+#include "amduat/hash/asl1.h"
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static int failures = 0;
+
+static void expect(bool cond, const char *msg) {
+  if (!cond) {
+    fprintf(stderr, "FAIL: %s\n", msg);
+    failures++;
+  }
+}
+
+int main(void) {
+  amduatd_fed_cfg_t cfg;
+  amduatd_space_t space;
+  amduat_octets_t scoped = amduat_octets(NULL, 0u);
+  uint8_t digest_bytes[32];
+  amduat_octets_t digest;
+  amduat_reference_t ref;
+  char *ref_hex = NULL;
+  const char *err = NULL;
+  int i;
+
+  memset(digest_bytes, 0x2a, sizeof(digest_bytes));
+  if (!amduat_octets_clone(amduat_octets(digest_bytes, sizeof(digest_bytes)),
+                           &digest)) {
+    fprintf(stderr, "FAIL: digest clone\n");
+    return 1;
+  }
+
+  ref = amduat_reference(AMDUAT_HASH_ASL1_ID_SHA256, digest);
+  if (!amduat_asl_ref_encode_hex(ref, &ref_hex)) {
+    fprintf(stderr, "FAIL: ref encode\n");
+    amduat_reference_free(&ref);
+    return 1;
+  }
+
+  amduatd_fed_cfg_init(&cfg);
+  expect(!cfg.enabled, "default disabled");
+  expect(cfg.transport_kind == AMDUATD_FED_TRANSPORT_STUB, "default transport");
+  expect(!cfg.require_space, "default require_space");
+
+  {
+    char *argv[] = {
+        "amduatd",
+        "--fed-enable",
+        "--fed-transport",
+        "unix",
+        "--fed-unix-sock",
+        "amduatd.sock",
+        "--fed-domain-id",
+        "42",
+        "--fed-registry-ref",
+        ref_hex,
+        "--fed-require-space",
+    };
+    int argc = (int)(sizeof(argv) / sizeof(argv[0]));
+    for (i = 1; i < argc; ++i) {
+      amduatd_fed_parse_result_t rc;
+      rc = amduatd_fed_cfg_parse_arg(&cfg, argc, argv, &i, &err);
+      expect(rc == AMDUATD_FED_PARSE_OK, "fed parse ok");
+    }
+  }
+
+  expect(cfg.enabled, "parsed enabled");
+  expect(cfg.transport_kind == AMDUATD_FED_TRANSPORT_UNIX,
+         "parsed transport");
+  expect(cfg.unix_socket_set, "parsed unix socket");
+  expect(cfg.local_domain_id == 42u, "parsed domain id");
+  expect(cfg.registry_ref_set, "parsed registry ref");
+  expect(cfg.require_space, "parsed require space");
+
+  expect(!amduatd_fed_requirements_check(AMDUATD_STORE_BACKEND_FS,
+                                         &cfg,
+                                         &err),
+         "requirements reject fs backend");
+  expect(amduatd_fed_requirements_check(AMDUATD_STORE_BACKEND_INDEX,
+                                        &cfg,
+                                        &err),
+         "requirements accept index backend");
+
+  if (!amduatd_space_init(&space, NULL, false)) {
+    fprintf(stderr, "FAIL: space init\n");
+    amduatd_fed_cfg_free(&cfg);
+    amduat_reference_free(&ref);
+    free(ref_hex);
+    return 1;
+  }
+  expect(!amduatd_fed_scope_names(&cfg, &space, "fed", &scoped, &err),
+         "scope requires space");
+  amduat_octets_free(&scoped);
+
+  if (!amduatd_space_init(&space, "alpha", false)) {
+    fprintf(stderr, "FAIL: space init alpha\n");
+    amduatd_fed_cfg_free(&cfg);
+    amduat_reference_free(&ref);
+    free(ref_hex);
+    return 1;
+  }
+  expect(amduatd_fed_scope_names(&cfg, &space, "fed", &scoped, &err),
+         "scope with space");
+  expect(scoped.data != NULL &&
+             scoped.len == strlen("space/alpha/fed") &&
+             memcmp(scoped.data,
+                    "space/alpha/fed",
+                    scoped.len) == 0,
+         "scoped name");
+  amduat_octets_free(&scoped);
+
+  amduatd_fed_cfg_free(&cfg);
+  amduat_reference_free(&ref);
+  free(ref_hex);
+  return failures == 0 ? 0 : 1;
+}