[PATCH 06/10] net: lwip: add an HTTP client abort operation

The HTTP client has no public way to cancel a request. Returning from
wget while DNS or TCP work remains pending can therefore leave callbacks
referencing its released command state.

Track pending DNS resolution and add httpc_abort(). The operation removes
a pending DNS callback, detaches the HTTP callbacks and immediately
aborts the altcp connection. Report a local abort through the normal
result callback.

Signed-off-by: James Hilliard <[email protected]>
---
 lib/lwip/lwip/src/apps/http/http_client.c         | 71 ++++++++++++++++++++---
 lib/lwip/lwip/src/include/lwip/apps/http_client.h |  1 +
 2 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/lib/lwip/lwip/src/apps/http/http_client.c b/lib/lwip/lwip/src/apps/http/http_client.c
index 1973e79e723..2bc2a0db97e 100644
--- a/lib/lwip/lwip/src/apps/http/http_client.c
+++ b/lib/lwip/lwip/src/apps/http/http_client.c
@@ -146,15 +146,23 @@ typedef struct _httpc_state
   u32_t rx_content_len;
   u32_t hdr_content_len;
   httpc_parse_state_t parse_state;
+#if LWIP_DNS
+  u8_t dns_pending;
+#endif
 #if HTTPC_DEBUG_REQUEST
   char* server_name;
   char* uri;
 #endif
 } httpc_state_t;
 
-/** Free http client state and deallocate all resources within */
-static err_t
-httpc_free_state(httpc_state_t* req)
+#if LWIP_DNS
+static void httpc_dns_found(const char* hostname, const ip_addr_t *ipaddr,
+                            void *arg);
+#endif
+
+/** Free http client state and detach its connection callbacks */
+static struct altcp_pcb *
+httpc_detach_state(httpc_state_t* req)
 {
   struct altcp_pcb* tpcb;
 
@@ -168,16 +176,26 @@ httpc_free_state(httpc_state_t* req)
   }
 
   tpcb = req->pcb;
-  mem_free(req);
-  req = NULL;
-
   if (tpcb != NULL) {
-    err_t r;
     altcp_arg(tpcb, NULL);
     altcp_recv(tpcb, NULL);
     altcp_err(tpcb, NULL);
     altcp_poll(tpcb, NULL, 0);
     altcp_sent(tpcb, NULL);
+  }
+  mem_free(req);
+  return tpcb;
+}
+
+/** Free http client state and deallocate all resources within */
+static err_t
+httpc_free_state(httpc_state_t* req)
+{
+  struct altcp_pcb* tpcb;
+
+  tpcb = httpc_detach_state(req);
+  if (tpcb != NULL) {
+    err_t r;
     r = altcp_close(tpcb);
     if (r != ERR_OK) {
       altcp_abort(tpcb);
@@ -202,6 +220,38 @@ httpc_close(httpc_state_t* req, httpc_result_t result, u32_t server_response, er
   return ERR_OK;
 }
 
+/** Abort an HTTP client request. */
+err_t
+httpc_abort(httpc_state_t *req)
+{
+  struct altcp_pcb *tpcb;
+
+  if (req == NULL) {
+    return ERR_ARG;
+  }
+
+#if LWIP_DNS
+  if (req->dns_pending) {
+    dns_cancel(httpc_dns_found, req);
+    req->dns_pending = 0;
+  }
+#endif
+
+  if (req->conn_settings != NULL) {
+    if (req->conn_settings->result_fn != NULL) {
+      req->conn_settings->result_fn(req->callback_arg,
+        HTTPC_RESULT_LOCAL_ABORT, req->rx_content_len, 0, ERR_ABRT);
+    }
+  }
+
+  tpcb = httpc_detach_state(req);
+  if (tpcb != NULL) {
+    altcp_abort(tpcb);
+  }
+
+  return ERR_OK;
+}
+
 /** Parse http header response line 1 */
 static err_t
 http_parse_response_status(struct pbuf *p, u16_t *http_version, u16_t *http_status, u16_t *http_status_str_offset)
@@ -447,6 +497,7 @@ httpc_dns_found(const char* hostname, const ip_addr_t *ipaddr, void *arg)
 
   LWIP_UNUSED_ARG(hostname);
 
+  req->dns_pending = 0;
   if (ipaddr != NULL) {
     err = httpc_get_internal_addr(req, ipaddr);
     if (err == ERR_OK) {
@@ -479,9 +530,13 @@ httpc_get_internal_dns(httpc_state_t* req, const char* server_name)
   if (err == ERR_OK) {
     /* cached or IP-string */
     err = httpc_get_internal_addr(req, &req->remote_addr);
-  } else if (err == ERR_INPROGRESS) {
+  }
+#if LWIP_DNS
+  else if (err == ERR_INPROGRESS) {
+    req->dns_pending = 1;
     return ERR_OK;
   }
+#endif
   return err;
 }
 
diff --git a/lib/lwip/lwip/src/include/lwip/apps/http_client.h b/lib/lwip/lwip/src/include/lwip/apps/http_client.h
index d39e1bf829a..3f62150dca1 100644
--- a/lib/lwip/lwip/src/include/lwip/apps/http_client.h
+++ b/lib/lwip/lwip/src/include/lwip/apps/http_client.h
@@ -143,6 +143,7 @@ err_t httpc_get_file(const ip_addr_t* server_addr, u16_t port, const char* uri,
                      altcp_recv_fn recv_fn, void* callback_arg, httpc_state_t **connection);
 err_t httpc_get_file_dns(const char* server_name, u16_t port, const char* uri, const httpc_connection_t *settings,
                      altcp_recv_fn recv_fn, void* callback_arg, httpc_state_t **connection);
+err_t httpc_abort(httpc_state_t *connection);
 
 #if LWIP_HTTPC_HAVE_FILE_IO
 err_t httpc_get_file_to_disk(const ip_addr_t* server_addr, u16_t port, const char* uri, const httpc_connection_t *settings,

-- 
2.53.0