feat(esp_netif): PPP: Use RAM allocated pbufs instead of POOL (fixed size)

PPP netif: Used allocated packet buffers of exact size
for input to TCP/IP stack to consume less memory in download mode
(compared to the previously used fixed sized packet buffers)

components/esp_netif/CMakeLists.txt

@@ -24,7 +24,7 @@ if(${target} STREQUAL "linux")
 endif()
 
 if(CONFIG_PPP_SUPPORT)
-    list(APPEND srcs_lwip lwip/esp_netif_lwip_ppp.c)
+    list(APPEND srcs_lwip lwip/esp_netif_lwip_ppp.c lwip/netif/ppp.c)
 endif()
 
 

components/esp_netif/lwip/esp_netif_lwip_ppp.c

@@ -17,6 +17,7 @@
 #include "esp_netif_lwip_internal.h"
 #include <string.h>
 #include "lwip/ip6_addr.h"
+#include "netif/pppif.h"
 
 ESP_EVENT_DEFINE_BASE(NETIF_PPP_STATUS);
 
@@ -285,7 +286,7 @@ esp_err_t esp_netif_start_ppp(esp_netif_t *esp_netif)
 esp_netif_recv_ret_t esp_netif_lwip_ppp_input(void *ppp_ctx, void *buffer, size_t len, void *eb)
 {
     struct lwip_peer2peer_ctx * obj = ppp_ctx;
-    err_t ret = pppos_input_tcpip(obj->ppp, buffer, len);
+    err_t ret = pppos_input_tcpip_as_ram_pbuf(obj->ppp, buffer, len);
     if (ret != ERR_OK) {
         ESP_LOGE(TAG, "pppos_input_tcpip failed with %d", ret);
         return ESP_NETIF_OPTIONAL_RETURN_CODE(ESP_FAIL);

components/esp_netif/lwip/netif/ppp.c

@@ -0,0 +1,28 @@
+/*
+ * SPDX-FileCopyrightText: 2001-2004 Swedish Institute of Computer Science
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * SPDX-FileContributor: 2023 Espressif Systems (Shanghai) CO LTD
+ */
+#include "pppif.h"
+#include "lwip/tcpip.h"
+
+/*
+ * Similar to pppos_input_tcpip() from lwip's ppp netif, but instead
+ * of PBUF_POOL, we use PBUF_RAM type of the pbuf we pass to the stack
+ */
+err_t pppos_input_tcpip_as_ram_pbuf(ppp_pcb *ppp, u8_t *s, int l)
+{
+    struct pbuf *p = pbuf_alloc(PBUF_RAW, l, PBUF_RAM);
+    if (!p) {
+        return ERR_MEM;
+    }
+    pbuf_take(p, s, l);
+
+    err_t err = tcpip_inpkt(p, ppp_netif(ppp), pppos_input_sys);
+    if (err != ERR_OK) {
+        pbuf_free(p);
+    }
+    return err;
+}

components/esp_netif/lwip/netif/pppif.h

@@ -0,0 +1,22 @@
+/*
+ * SPDX-FileCopyrightText: 2001-2004 Swedish Institute of Computer Science
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * SPDX-FileContributor: 2023 Espressif Systems (Shanghai) CO LTD
+ */
+#include "lwip/pbuf.h"
+#include "netif/ppp/pppos.h"
+
+/** Pass received raw characters to PPPoS to be decoded through lwIP TCPIP thread.
+ *
+ * This function uses allocated packet buffers of exact size for input to TCP/IP stack
+ * to consume less memory in download mode, compared to the pppos_input_tcpip() from lwIP.
+ * (original implementation uses `PBUF_POOL`, which on ESP port uses standard malloc
+ * to allocate a fixed size pbuf)
+ *
+ * @param ppp PPP descriptor index, returned by pppos_create()
+ * @param s received data
+ * @param l length of received data
+ */
+ err_t pppos_input_tcpip_as_ram_pbuf(ppp_pcb *ppp, u8_t *s, int l);