fix(libraries/asyncudp): IPv4 ONLY listenMulticast() (espressif#11444)

AsyncUDP::listenMulticast() properly receives packets sent to IPv4 multicast addresses like 239.1.2.3, but it is not receiving packets sent to IPv6 multicast addresses like ff12::6ood:cafe. The root cause is a bit hidden: listen(NULL, port) would match AsyncUDP::listen(const ip_addr_t *addr, uint16_t port), which calls _udp_bind(_pcb, addr, port), which uses the lwIP API to call udp_bind(struct udp_pcb *pcb, const ip_addr_t *ipaddr, u16_t port) at the end. If lwIP has LWIP_IPV4 enabled, it checks if ipaddr == NULL and sets it to IP4_ADDR_ANY. So an IPv6 address is never bound. This fix checks the IP address passed to AsyncUDP::listenMulticast(). If it is an IPv6 address, it constructs and passes the IPv6 any address (::); otherwise (IPv4), it constructs and passes the IPv4 any address (0.0.0.0).

Author: nikiwaibel

libraries/AsyncUDP/src/AsyncUDP.cpp

@@ -682,6 +682,8 @@ static esp_err_t joinMulticastGroup(const ip_addr_t *addr, bool join, tcpip_adap
 }
 
 bool AsyncUDP::listenMulticast(const ip_addr_t *addr, uint16_t port, uint8_t ttl, tcpip_adapter_if_t tcpip_if) {
+ ip_addr_t bind_addr;
+
  if (!ip_addr_ismulticast(addr)) {
  return false;
  }
@@ -690,7 +692,18 @@ bool AsyncUDP::listenMulticast(const ip_addr_t *addr, uint16_t port, uint8_t ttl
  return false;
  }
 
- if (!listen(NULL, port)) {
+#if CONFIG_LWIP_IPV6
+ if (IP_IS_V6(addr)) {
+ IP_SET_TYPE(&bind_addr, IPADDR_TYPE_V6);
+ ip6_addr_set_any(&bind_addr.u_addr.ip6);
+ } else {
+#endif
+ IP_SET_TYPE(&bind_addr, IPADDR_TYPE_V4);
+ ip4_addr_set_any(&bind_addr.u_addr.ip4);
+#if CONFIG_LWIP_IPV6
+ }
+#endif
+ if (!listen(&bind_addr, port)) {
  return false;
  }