nanocoap: implement extended tokens (RFC 8974)

sys/include/net/nanocoap.h

@@ -91,6 +91,7 @@
 #include "byteorder.h"
 #include "iolist.h"
 #include "net/coap.h"
+#include "modules.h"
 #else
 #include "coap.h"
 #include <arpa/inet.h>
@@ -494,15 +495,37 @@ static inline unsigned coap_get_id(const coap_pkt_t *pkt)
 /**
  * @brief   Get a message's token length [in byte]
  *
+ * If the `nanocoap_token_ext` module is enabled, this will include
+ * the extended token length.
+ *
  * @param[in]   pkt   CoAP packet
  *
  * @returns     length of token in the given message (0-8 byte)
  */
 static inline unsigned coap_get_token_len(const coap_pkt_t *pkt)
 {
-    return (pkt->hdr->ver_t_tkl & 0xf);
+    uint8_t tkl = pkt->hdr->ver_t_tkl & 0xf;
+
+    if (!IS_USED(MODULE_NANOCOAP_TOKEN_EXT)) {
+        return tkl;
+    }
+
+    void *ext = pkt->hdr + 1;
+    switch (tkl) {
+    case 13:
+        return tkl + *(uint8_t *)ext;
+    case 14:
+        return tkl + 255 + byteorder_bebuftohs(ext);
+    case 15:
+        assert(0);
+        /* fall-through */
+    default:
+        return tkl;
+    }
 }
 
+static inline uint8_t *coap_hdr_data_ptr(const coap_hdr_t *hdr);
+
 /**
  * @brief   Get pointer to a message's token
  *
@@ -512,7 +535,7 @@ static inline unsigned coap_get_token_len(const coap_pkt_t *pkt)
  */
 static inline void *coap_get_token(const coap_pkt_t *pkt)
 {
-    return (uint8_t*)pkt->hdr + sizeof(coap_hdr_t);
+    return coap_hdr_data_ptr(pkt->hdr);
 }
 
 /**
@@ -568,6 +591,35 @@ static inline unsigned coap_get_ver(const coap_pkt_t *pkt)
     return (pkt->hdr->ver_t_tkl & 0x60) >> 6;
 }
 
+/**
+ * @brief   Get the size of the extended Token length field
+ *          (RFC 8974)
+ *
+ * @note    This requires the `nanocoap_token_ext` module to be enabled
+ *
+ * @param[in]   hdr   CoAP header
+ *
+ * @returns     number of bytes used for extended token length
+ */
+static inline uint8_t coap_hdr_tkl_ext_len(const coap_hdr_t *hdr)
+{
+    if (!IS_USED(MODULE_NANOCOAP_TOKEN_EXT)) {
+        return 0;
+    }
+
+    switch (hdr->ver_t_tkl & 0xf) {
+    case 13:
+        return 1;
+    case 14:
+        return 2;
+    case 15:
+        assert(0);
+        /* fall-through */
+    default:
+        return 0;
+    }
+}
+
 /**
  * @brief   Get the start of data after the header
  *
@@ -577,7 +629,7 @@ static inline unsigned coap_get_ver(const coap_pkt_t *pkt)
  */
 static inline uint8_t *coap_hdr_data_ptr(const coap_hdr_t *hdr)
 {
-    return ((uint8_t *)hdr) + sizeof(coap_hdr_t);
+    return ((uint8_t *)hdr) + sizeof(coap_hdr_t) + coap_hdr_tkl_ext_len(hdr);
 }
 
 /**

sys/net/application_layer/nanocoap/nanocoap.c

@@ -80,7 +80,13 @@ int coap_parse(coap_pkt_t *pkt, uint8_t *buf, size_t len)
         return -EBADMSG;
     }
 
-    if (coap_get_token_len(pkt) > COAP_TOKEN_LENGTH_MAX) {
+    if (IS_USED(MODULE_NANOCOAP_TOKEN_EXT)) {
+        if ((pkt->hdr->ver_t_tkl & 0xf) == 15) {
+            DEBUG("nanocoap: token length is reserved value 15,"
+                  "invalid for extended token length field.\n");
+            return -EBADMSG;
+        }
+    } else if (coap_get_token_len(pkt) > COAP_TOKEN_LENGTH_MAX) {
         DEBUG("nanocoap: token length invalid\n");
         return -EBADMSG;
     }
@@ -555,18 +561,39 @@ ssize_t coap_build_reply(coap_pkt_t *pkt, unsigned code,
 ssize_t coap_build_hdr(coap_hdr_t *hdr, unsigned type, uint8_t *token, size_t token_len, unsigned code, uint16_t id)
 {
     assert(!(type & ~0x3));
-    assert(!(token_len & ~0x1f));
+
+    uint16_t tkl_ext;
+    uint8_t tkl_ext_len, tkl;
+
+    if (token_len > 268 && IS_USED(MODULE_NANOCOAP_TOKEN_EXT)) {
+        tkl_ext_len = 2;
+        tkl_ext = htons(token_len - 269); /* 269 = 255 + 14 */
+        tkl = 14;
+    }
+    else if (token_len > 12 && IS_USED(MODULE_NANOCOAP_TOKEN_EXT)) {
+        tkl_ext_len = 1;
+        tkl_ext = token_len - 13;
+        tkl = 13;
+    }
+    else {
+        tkl = token_len;
+        tkl_ext_len = 0;
+    }
 
     memset(hdr, 0, sizeof(coap_hdr_t));
-    hdr->ver_t_tkl = (COAP_V1 << 6) | (type << 4) | token_len;
+    hdr->ver_t_tkl = (COAP_V1 << 6) | (type << 4) | tkl;
     hdr->code = code;
     hdr->id = htons(id);
 
+    if (tkl_ext_len) {
+        memcpy(hdr + 1, &tkl_ext, tkl_ext_len);
+    }
+
     if (token_len) {
         memcpy(coap_hdr_data_ptr(hdr), token, token_len);
     }
 
-    return sizeof(coap_hdr_t) + token_len;
+    return sizeof(coap_hdr_t) + token_len + tkl_ext_len;
 }
 
 void coap_pkt_init(coap_pkt_t *pkt, uint8_t *buf, size_t len, size_t header_len)