extmod/network_lwip: Add sys_untimeout_all_with_arg helper function.

Really lwIP should provide this, to deregister all callbacks on the given
netif.

Signed-off-by: Damien George <damien@micropython.org>

extmod/lwip-include/lwipopts_common.h

@@ -28,6 +28,9 @@
 
 #include "py/mpconfig.h"
 
+// This is needed to access `next_timeout` via `sys_timeouts_get_next_timeout()`.
+#define LWIP_TESTMODE                   1
+
 // This sys-arch protection is not needed.
 // Ports either protect lwIP code with flags, or run it at PendSV priority.
 #define SYS_ARCH_DECL_PROTECT(lev) do { } while (0)

extmod/modnetwork.h

@@ -82,6 +82,9 @@ extern const struct _mp_obj_type_t mp_network_ppp_lwip_type;
 #endif
 
 struct netif;
+
+void sys_untimeout_all_with_arg(void *arg);
+
 void mod_network_lwip_init(void);
 void mod_network_lwip_poll_wrapper(uint32_t ticks_ms);
 mp_obj_t mod_network_nic_ifconfig(struct netif *netif, size_t n_args, const mp_obj_t *args);

extmod/network_lwip.c

@@ -52,6 +52,19 @@ int mp_mod_network_prefer_dns_use_ip_version = 4;
 
 // Implementations of network methods that can be used by any interface.
 
+// This follows sys_untimeout but removes all timeouts with the given argument.
+void sys_untimeout_all_with_arg(void *arg) {
+    for (struct sys_timeo **t = sys_timeouts_get_next_timeout(); *t != NULL;) {
+        if ((*t)->arg == arg) {
+            struct sys_timeo *next = (*t)->next;
+            memp_free(MEMP_SYS_TIMEOUT, *t);
+            *t = next;
+        } else {
+            t = &(*t)->next;
+        }
+    }
+}
+
 // This function provides the implementation of nic.ifconfig, is deprecated and will be removed.
 // Use network.ipconfig and nic.ipconfig instead.
 mp_obj_t mod_network_nic_ifconfig(struct netif *netif, size_t n_args, const mp_obj_t *args) {