app: http: Handle "Connection: close" header in HTTP response

Add <connection_close> field to #XHTTPCSTAT URC to indicate when
the server signals connection closure via the "Connection: close"
header.

XHTTPCSTAT: <handle>,<status_code>,<bytes>,<connection_close>

When <connection_close> is set, the host must close and reopen the
socket before sending the next request.

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

Author: juhaylinen

app/src/sm_at_httpc.c

@@ -82,6 +82,7 @@ struct http_request {
 	struct modem_pipe *pipe;    /* AT pipe that created this request */
 	bool manual_mode;           /* Manual mode: body not auto-received, host pulls chunks */
 	int bytes_sent;             /* Response-body bytes sent to the host */
+	bool connection_close;      /* Server sent "Connection: close" header */
 };
 
 static const char * const http_method_str[] = {
@@ -105,6 +106,7 @@ static bool http_headers_complete(struct http_request *req, char *header_end,
 				  struct sm_socket *sock, bool hup);
 static int parse_http_status_code(const char *buf, int *status_code);
 static int parse_content_length(const char *buf, const char *header_end, int *length);
+static bool parse_connection_close(const char *buf, const char *header_end);
 static void http_timeout_work_fn(struct k_work *work);
 
 static K_MUTEX_DEFINE(http_mutex);
@@ -433,20 +435,22 @@ static void http_close_request(struct http_request *req)
 /* Send error via XHTTPCSTAT with -1 status code */
 static void http_send_error(struct http_request *req)
 {
-	urc_send_to(req->pipe, "\r\n#XHTTPCSTAT: %d,-1,%d\r\n", req->fd, req->total_received);
+	urc_send_to(req->pipe, "\r\n#XHTTPCSTAT: %d,-1,%d,%d\r\n", req->fd,
+		 req->total_received, (int)req->connection_close);
 }
 
 /* Send status URC */
 static void http_send_status(struct http_request *req)
 {
-	urc_send_to(req->pipe, "\r\n#XHTTPCSTAT: %d,%d,%d\r\n", req->fd, req->status_code,
-		 req->total_received);
+	urc_send_to(req->pipe, "\r\n#XHTTPCSTAT: %d,%d,%d,%d\r\n", req->fd, req->status_code,
+		 req->total_received, (int)req->connection_close);
 }
 
 /* Send cancel status URC with bytes already delivered to host */
 static void http_send_cancel_status(struct http_request *req)
 {
-	urc_send_to(req->pipe, "\r\n#XHTTPCSTAT: %d,-1,%d\r\n", req->fd, req->bytes_sent);
+	urc_send_to(req->pipe, "\r\n#XHTTPCSTAT: %d,-1,%d,%d\r\n", req->fd,
+		 req->bytes_sent, (int)req->connection_close);
 }
 
 /* Send error and close request */
@@ -511,6 +515,19 @@ static int parse_http_status_code(const char *buf, int *status_code)
 	return 0;
 }
 
+/* Parse Connection: close header from response buffer */
+static bool parse_connection_close(const char *buf, const char *header_end)
+{
+	const char *p;
+
+	p = strstr(buf, "Connection: close");
+	if (!p) {
+		p = strstr(buf, "connection: close");
+	}
+
+	return p != NULL && p < header_end;
+}
+
 /* Parse Content-Length header from response buffer */
 static int parse_content_length(const char *buf, const char *header_end, int *length)
 {
@@ -563,6 +580,11 @@ static bool http_headers_complete(struct http_request *req, char *header_end,
 		LOG_DBG("HTTP %d: No Content-Length header", req->fd);
 	}
 
+	req->connection_close = parse_connection_close((char *)req->recv_buf, header_end);
+	if (req->connection_close) {
+		LOG_INF("HTTP %d: Server sent Connection: close", req->fd);
+	}
+
 	req->headers_complete = true;
 	req->state = HTTP_STATE_RECEIVING_BODY;
 
@@ -707,22 +729,26 @@ static void http_process_request(struct http_request *req, uint8_t events)
 	case HTTP_STATE_RECEIVING_BODY:
 		/* POLLHUP without POLLIN before headers are received is an error:
 		 * the server closed the connection before sending a valid response.
+		 * When POLLIN co-fires, data may still be in the socket buffer (e.g.
+		 * a server with Connection: close that sends headers and closes
+		 * simultaneously); fall through to the POLLIN handler to drain it.
 		 */
 		if (events & NRF_POLLHUP) {
-			if (!req->headers_complete) {
-				/* Server closed before headers arrived */
+			if (!req->headers_complete && !(events & NRF_POLLIN)) {
+				/* Server closed before headers arrived and no data to read */
 				LOG_ERR("HTTP %d: Connection closed before headers (POLLHUP)",
 					req->fd);
 				http_fail_request(req);
 				return;
 			}
-			if (!(events & NRF_POLLIN)) {
+			if (req->headers_complete && !(events & NRF_POLLIN)) {
 				/* POLLHUP alone during body reception: server closed cleanly
-				 * after all data.  Treat as EOF.
+				 * after all data. Treat as EOF.
 				 */
 				if (req->state == HTTP_STATE_RECEIVING_BODY) {
 					if (req->content_length > 0 &&
-					    req->total_received < req->content_length)
+					    req->total_received < req->content_length &&
+					    !req->connection_close)
 						LOG_WRN("HTTP %d: Incomplete - %d/%d bytes",
 							req->fd, req->total_received,
 							req->content_length);
@@ -768,7 +794,8 @@ static void http_process_request(struct http_request *req, uint8_t events)
 
 				/* Check if we received all expected data */
 				if (req->content_length > 0 &&
-				    req->total_received < req->content_length) {
+				    req->total_received < req->content_length &&
+				    !req->connection_close) {
 					LOG_WRN("HTTP %d: Incomplete transfer - received %d/%d "
 						"bytes",
 						req->fd, req->total_received,

doc/app/at_httpc.rst

@@ -134,7 +134,7 @@ The notification line is terminated with ``\r\n`` and the raw body bytes follow
 
 ``#XHTTPCSTAT`` is emitted when the request completes, fails, or is cancelled::
 
-   #XHTTPCSTAT: <handle>,<status_code>,<total_bytes>
+   #XHTTPCSTAT: <handle>,<status_code>,<total_bytes>,<connection_close>
 
 * The ``<handle>`` parameter is an integer.
   It identifies the socket.
@@ -144,6 +144,10 @@ The notification line is terminated with ``\r\n`` and the raw body bytes follow
    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.
+* The ``<connection_close>`` parameter is an integer.
+  It is ``1`` when the server included a ``Connection: close`` header in its response, indicating that the TCP connection will be closed after this response.
+  It is ``0`` otherwise (keep-alive connection).
+  When ``<connection_close>`` is ``1``, the host must close the socket with ``AT#XCLOSE`` and open a new connection before issuing the next request.
 
 .. note::
 
@@ -169,7 +173,7 @@ HTTP GET (automatic mode):
    #XHTTPCDATA: 0,0,261
    <261 bytes>
 
-   #XHTTPCSTAT: 0,200,261
+   #XHTTPCSTAT: 0,200,261,0
 
 HTTP GET (manual mode):
 
@@ -186,7 +190,7 @@ HTTP GET (manual mode):
    <261 bytes>
    OK
 
-   #XHTTPCSTAT: 0,200,261
+   #XHTTPCSTAT: 0,200,261,0
 
 HTTP POST with JSON body and custom header:
 
@@ -203,10 +207,12 @@ HTTP POST with JSON body and custom header:
    #XHTTPCDATA: 0,0,432
    <432 bytes>
 
-   #XHTTPCSTAT: 0,200,432
+   #XHTTPCSTAT: 0,200,432,0
 
 HTTP GET with Range header (``body_len=0`` is required as a placeholder when headers follow a GET):
 
+In this example the server returns ``connection_close=1``, so the host must close and reopen the socket before the next request.
+
 ::
 
    AT#XHTTPCREQ=0,<url>,0,1,0,"Range: bytes=0-127"
@@ -218,7 +224,7 @@ HTTP GET with Range header (``body_len=0`` is required as a placeholder when hea
    #XHTTPCDATA: 0,0,128
    <128 bytes>
 
-   #XHTTPCSTAT: 0,206,128
+   #XHTTPCSTAT: 0,206,128,0
 
    AT#XHTTPCREQ=0,<url>,0,1,0,"Range: bytes=128-255"
    #XHTTPCREQ: 0
@@ -229,7 +235,7 @@ HTTP GET with Range header (``body_len=0`` is required as a placeholder when hea
    #XHTTPCDATA: 0,0,128
    <128 bytes>
 
-   #XHTTPCSTAT: 0,206,128
+   #XHTTPCSTAT: 0,206,128,1
 
 
 HTTP HEAD (no body — ``#XHTTPCSTAT`` follows immediately after ``#XHTTPCHEAD``):
@@ -242,7 +248,7 @@ HTTP HEAD (no body — ``#XHTTPCSTAT`` follows immediately after ``#XHTTPCHEAD``
 
    #XHTTPCHEAD: 0,200,261
 
-   #XHTTPCSTAT: 0,200,0
+   #XHTTPCSTAT: 0,200,0,0
 
 HTTP POST with chunked response (``content_length=-1``):
 
@@ -259,7 +265,7 @@ HTTP POST with chunked response (``content_length=-1``):
    #XHTTPCDATA: 0,0,1132
    460\r\n{"args":{},"data":"<1024 bytes>","url":"..."}\r\n0\r\n\r\n
 
-   #XHTTPCSTAT: 0,200,1132
+   #XHTTPCSTAT: 0,200,1132,0
 
 .. note::
 
@@ -372,7 +378,7 @@ Example
    <256 bytes>
    OK
 
-   #XHTTPCSTAT: 0,200,512
+   #XHTTPCSTAT: 0,200,512,0
 
 Test command
 ------------
@@ -412,7 +418,7 @@ The timer resets each time data is sent or received:
 * Receiving response headers or body bytes.
 * Pulling a body chunk in manual mode (``AT#XHTTPCDATA``).
 
-If no such activity occurs within the configured window, the request is aborted and ``#XHTTPCSTAT: <handle>,-1,<total_bytes>`` is emitted.
+If no such activity occurs within the configured window, the request is aborted and ``#XHTTPCSTAT: <handle>,-1,<total_bytes>,<connection_close>`` is emitted.
 The timeout is enforced by a background timer that fires independently of normal socket poll events, so a server that stalls silently (no TCP RST or FIN) is also detected.
 
 HTTP request cancel #XHTTPCCANCEL
@@ -435,7 +441,7 @@ Syntax
 * The ``<handle>`` parameter is an integer.
   It identifies the socket of the request to cancel.
 
-An unsolicited ``#XHTTPCSTAT: <handle>,-1,<total_bytes>`` notification is emitted after cancellation, where ``<total_bytes>`` is the number of response body bytes already delivered to the host.
+An unsolicited ``#XHTTPCSTAT: <handle>,-1,<total_bytes>,<connection_close>`` notification is emitted after cancellation, where ``<total_bytes>`` is the number of response body bytes already delivered to the host.
 
 Example
 ~~~~~~~
@@ -444,7 +450,7 @@ Example
 
    AT#XHTTPCCANCEL=0
    OK
-   #XHTTPCSTAT: 0,-1,0
+   #XHTTPCSTAT: 0,-1,0,0
 
 Test command
 ------------