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fix(libraries/asyncudp): IPv4 ONLY listenMulticast() #11444
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fix(libraries/asyncudp): IPv4 ONLY listenMulticast() #11444
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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).
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Test Results 76 files 76 suites 12m 44s ⏱️ Results for commit 57f2ba7. |
Memory usage test (comparing PR against master branch)The table below shows the summary of memory usage change (decrease - increase) in bytes and percentage for each target.
Click to expand the detailed deltas report [usage change in BYTES]
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Description of Change
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).
Tests scenarios
I've tested my Pull Request on Arduino-esp32 core v3.2.0 with a Heltec v3 (ESP32-S3) board.
Related links
Fixes #9970 (it was auto-closed).
In PR #11443 i've used a branch name with uppercase letters, which produced some warnings.