app: http: Handle HTTP chunked transfer encoding

Detect HTTP/1.1 chunked transfer EOF marker in a body data buffer.
Update documentation.

Signed-off-by: Juha Ylinen <juha.ylinen@nordicsemi.no>

Author: juhaylinen

app/src/sm_at_httpc.c

@@ -482,6 +482,15 @@ static void http_send_data(struct http_request *req, const uint8_t *data, int le
 	data_send(req->pipe, data, len);
 }
 
+/*
+ * Detect HTTP/1.1 chunked transfer EOF marker in a body data buffer.
+ * The final chunk is always "0\r\n\r\n" (zero-length chunk, RFC 9112 §7.1.1).
+ */
+static bool chunked_eof(const uint8_t *data, int len)
+{
+	return len >= 5 && memcmp(data + len - 5, "0\r\n\r\n", 5) == 0;
+}
+
 /* Parse HTTP status code from response buffer */
 static int parse_http_status_code(const char *buf, int *status_code)
 {
@@ -616,12 +625,14 @@ static bool http_headers_complete(struct http_request *req, char *header_end,
 	}
 
 	/*
-	 * All body bytes arrived piggybacked with the headers and
-	 * content-length is satisfied.  With keep-alive connections
-	 * there is no subsequent EOF to trigger the completion check
-	 * in the RECEIVING_BODY path, so finish here instead.
+	 * Finish early when all body data is already in hand (piggybacked):
+	 * either content-length is satisfied, or chunked terminator was received.
+	 * With keep-alive connections there is no subsequent EOF to trigger the
+	 * completion check in the RECEIVING_BODY path.
 	 */
-	if (req->content_length >= 0 && req->bytes_sent >= req->content_length) {
+	if ((req->content_length >= 0 && req->bytes_sent >= req->content_length) ||
+	    (req->content_length < 0 &&
+	     chunked_eof(req->recv_buf + body_offset, body_len))) {
 		http_finish_request(req);
 		return true;
 	}
@@ -697,11 +708,31 @@ static void http_process_request(struct http_request *req, uint8_t events)
 		/* POLLHUP without POLLIN before headers are received is an error:
 		 * the server closed the connection before sending a valid response.
 		 */
-		if ((events & NRF_POLLHUP) && !(events & NRF_POLLIN) &&
-		    !req->headers_complete) {
-			LOG_ERR("HTTP %d: Connection closed before headers (POLLHUP)", req->fd);
-			http_fail_request(req);
-			return;
+		if (events & NRF_POLLHUP) {
+			if (!req->headers_complete) {
+				/* Server closed before headers arrived */
+				LOG_ERR("HTTP %d: Connection closed before headers (POLLHUP)",
+					req->fd);
+				http_fail_request(req);
+				return;
+			}
+			if (!(events & NRF_POLLIN)) {
+				/* POLLHUP alone during body reception: server closed cleanly
+				 * after all data.  Treat as EOF.
+				 */
+				if (req->state == HTTP_STATE_RECEIVING_BODY) {
+					if (req->content_length > 0 &&
+					    req->total_received < req->content_length)
+						LOG_WRN("HTTP %d: Incomplete - %d/%d bytes",
+							req->fd, req->total_received,
+							req->content_length);
+					http_finish_request(req);
+					return;
+				}
+				/* In RECEIVING_HEADERS, fall through to the POLLIN
+				 * handler which may drain remaining bytes.
+				 */
+			}
 		}
 
 		/* Handle POLLIN */
@@ -786,14 +817,18 @@ static void http_process_request(struct http_request *req, uint8_t events)
 					xapoll_stop(sock);
 					return;
 				}
+				bool body_done = chunked_eof(req->recv_buf, req->recv_buf_len);
+
 				http_send_data(req, req->recv_buf, req->recv_buf_len);
 				req->recv_buf_len = 0;
 
-				/* Finish if content-length satisfied, or if the connection
-				 * is already closing (POLLHUP co-fired) — no point re-arming
-				 * POLLIN on a closing socket; nrf_recv would return EAGAIN.
+				/* Finish if:
+				 *  - content-length satisfied (known-length transfer)
+				 *  - chunked terminator "0\r\n\r\n" just received
+				 *  - POLLHUP co-fired (connection closing)
 				 */
-				if ((req->content_length > 0 &&
+				if (body_done ||
+				    (req->content_length > 0 &&
 				     req->bytes_sent >= req->content_length) ||
 				    (events & NRF_POLLHUP)) {
 					http_finish_request(req);

doc/app/at_httpc.rst

@@ -109,7 +109,7 @@ Unsolicited notification
 * The ``<status_code>`` parameter is an integer.
   It contains the HTTP status code returned by the server.
 * The ``<content_length>`` parameter is an integer.
-  It contains the value of the ``Content-Length`` response header, or ``-1`` when no such header is present.
+  It contains the value of the ``Content-Length`` response header, or ``-1`` when the server uses chunked transfer encoding or does not provide a content length.
 
 ``#XHTTPCDATA`` is emitted in automatic mode for each received body chunk::
 
@@ -124,6 +124,12 @@ The notification line is terminated with ``\r\n`` and the raw body bytes follow
 * The ``<length>`` parameter is an integer.
   It contains the number of body bytes in this chunk.
 
+.. note::
+
+   When the server uses ``Transfer-Encoding: chunked``, the body bytes delivered via ``#XHTTPCDATA`` include the raw chunked framing: each chunk is preceded by its size in hexadecimal followed by ``\r\n``, and followed by ``\r\n``.
+   The final zero-length chunk ``0\r\n\r\n`` is also forwarded.  The host is responsible for stripping this framing to recover the original body content.
+   The ``<total_bytes>`` field in ``#XHTTPCSTAT`` reflects the raw wire byte count including chunked framing, not the decoded body length.
+
 ``#XHTTPCSTAT`` is emitted when the request completes, fails, or is cancelled::
 
    #XHTTPCSTAT: <handle>,<status_code>,<total_bytes>
@@ -134,6 +140,7 @@ The notification line is terminated with ``\r\n`` and the raw body bytes follow
   It contains the HTTP status code on success, or ``-1`` on failure, cancel, or timeout.
 * The ``<total_bytes>`` parameter is an integer.
    On successful completion, failure, or timeout, it contains the total number of response body bytes received by the HTTP client.
+   For chunked transfer encoding this includes the raw framing bytes (chunk-size lines, ``\r\n`` separators, and the final ``0\r\n\r\n`` terminator).
    On cancel (``status_code=-1`` from ``AT#XHTTPCCANCEL``), it contains the number of response body bytes already delivered to the host.
 
 .. note::
@@ -235,6 +242,28 @@ HTTP HEAD (no body — ``#XHTTPCSTAT`` follows immediately after ``#XHTTPCHEAD``
 
    #XHTTPCSTAT: 0,200,0
 
+HTTP POST with chunked response (``content_length=-1``):
+
+::
+
+   AT#XHTTPCREQ=0,<url>,1,1,1024
+   #XHTTPCREQ: 0
+   OK
+   <1024 bytes payload>
+   #XDATAMODE: 0
+
+   #XHTTPCHEAD: 0,200,-1
+
+   #XHTTPCDATA: 0,0,1132
+   460\r\n{"args":{},"data":"<1024 bytes>","url":"..."}\r\n0\r\n\r\n
+
+   #XHTTPCSTAT: 0,200,1132
+
+.. note::
+
+   The 1132 raw bytes break down as chunked framing: ``460\r\n`` (chunk-size 1120 decimal in hex, 5 bytes), 1120 bytes of JSON body, ``\r\n`` (chunk trailer, 2 bytes), and ``0\r\n\r\n`` (final zero-length chunk, 5 bytes).
+   Strip this framing to recover the 1120-byte JSON body.
+
 Test command
 ------------
 
@@ -313,9 +342,13 @@ When the socket buffer is temporarily empty (EAGAIN)::
   It contains the number of body bytes delivered in this pull.
   A value of ``0`` means the socket buffer is currently empty.
 
-When all body bytes have been delivered, ``#XHTTPCSTAT`` is sent as a URC after
-the final ``OK``. This happens either when the server closes the connection, or
-when the ``Content-Length`` bytes have all been forwarded.
+When all body bytes have been delivered, ``#XHTTPCSTAT`` is sent as a URC after the final ``OK``.
+This happens either when the server closes the connection, when the ``Content-Length`` bytes have all been forwarded, or when the chunked transfer ``0\r\n\r\n`` terminator is received.
+
+.. note::
+
+   When the server uses ``Transfer-Encoding: chunked`` (``content_length=-1`` in ``#XHTTPCHEAD``), the bytes returned by ``#XHTTPCDATA`` include raw chunked framing.
+   See the note under ``#XHTTPCDATA`` in the ``AT#XHTTPCREQ`` section.
 
 .. note::