nanocoap/cache: Extend with option-only cache keygen

To generate cache keys based on only the options of a request. This for matching requests of a blockwise transfer with each other
RIOT-OS · Nov 2, 2023 · 984ecd9 · 984ecd9
1 parent 32795ca
commit 984ecd9
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Showing 2 changed files with 58 additions and 6 deletions.
diff --git a/sys/include/net/nanocoap/cache.h b/sys/include/net/nanocoap/cache.h
@@ -220,6 +220,26 @@ int nanocoap_cache_del(const nanocoap_cache_entry_t *ce);
  */
 void nanocoap_cache_key_generate(const coap_pkt_t *req, uint8_t *cache_key);
 
+/**
+ * @brief   Generates a cache key based on only the options in @p req
+ *
+ * @param[in] req           The request to generate the cache key from
+ * @param[out] cache_key    The generated cache key
+ */
+void nanocoap_cache_key_options_generate(const coap_pkt_t *req, uint8_t *cache_key);
+
+/**
+ * @brief   Generates a cache key based on only the options in @p req without
+ * any of the blockwise options included in the key
+ *
+ * This function can be used to correlate individual requests that are part of a
+ * blockwise transfer with each other.
+ *
+ * @param[in] req           The request to generate the cache key from
+ * @param[out] cache_key    The generated cache key
+ */
+void nanocoap_cache_key_blockreq_options_generate(const coap_pkt_t *req, uint8_t *cache_key);
+
 /**
  * @brief   Compares two cache keys.
  *

diff --git a/sys/net/application_layer/nanocoap/cache.c b/sys/net/application_layer/nanocoap/cache.c
@@ -83,11 +83,10 @@ size_t nanocoap_cache_free_count(void)
     return clist_count(&_empty_list_head);
 }
 
-void nanocoap_cache_key_generate(const coap_pkt_t *req, uint8_t *cache_key)
+static void _cache_key_digest_opts(const coap_pkt_t *req, sha256_context_t *ctx,
+        bool include_etag,
+        bool include_blockwise)
 {
-    sha256_context_t ctx;
-    sha256_init(&ctx);
-
     coap_optpos_t opt = {0, 0};
     uint8_t *value;
 
@@ -96,17 +95,50 @@ void nanocoap_cache_key_generate(const coap_pkt_t *req, uint8_t *cache_key)
         if (optlen >= 0) {
             /* gCoAP forward proxy is ETag-aware, so skip ETag option,
              * see https://datatracker.ietf.org/doc/html/rfc7252#section-5.4.2 */
-            if (IS_USED(MODULE_GCOAP_FORWARD_PROXY) && (opt.opt_num == COAP_OPT_ETAG)) {
+            if ((!include_etag) && (opt.opt_num == COAP_OPT_ETAG)) {
                 continue;
             }
             /* skip NoCacheKey,
                see https://tools.ietf.org/html/rfc7252#section-5.4.6 */
             if ((opt.opt_num & 0x1E) == 0x1C) {
                 continue;
             }
-            sha256_update(&ctx, value, optlen);
+            /* Don't include blockwise (on request) so matching between
+             * blockwise parts is possible */
+            if ((!include_blockwise) && (
+                    (opt.opt_num == COAP_OPT_BLOCK2) ||
+                    (opt.opt_num == COAP_OPT_BLOCK1)
+                    )) {
+                continue;
+            }
+            sha256_update(ctx, &opt.opt_num, sizeof(opt.opt_num));
+            sha256_update(ctx, value, optlen);
         }
     }
+}
+
+void nanocoap_cache_key_options_generate(const coap_pkt_t *req, uint8_t *cache_key)
+{
+    sha256_context_t ctx;
+    sha256_init(&ctx);
+    _cache_key_digest_opts(req, &ctx, true, true);
+    sha256_final(&ctx, cache_key);
+}
+
+void nanocoap_cache_key_blockreq_options_generate(const coap_pkt_t *req, uint8_t *cache_key)
+{
+    sha256_context_t ctx;
+    sha256_init(&ctx);
+    _cache_key_digest_opts(req, &ctx, true, false);
+    sha256_final(&ctx, cache_key);
+}
+
+void nanocoap_cache_key_generate(const coap_pkt_t *req, uint8_t *cache_key)
+{
+    sha256_context_t ctx;
+    sha256_init(&ctx);
+
+    _cache_key_digest_opts(req, &ctx, !(IS_USED(MODULE_GCOAP_FORWARD_PROXY)), true);
     switch (req->hdr->code) {
         case COAP_METHOD_FETCH:
             sha256_update(&ctx, req->payload, req->payload_len);