Mbed-os: UDPSocket::sendto does not work with ipv6 and local-link interface addresss

[slavaDev503]

Description

UDP socket can`t send data to ipv6 destination address. The project with mbed os 5.13.0 work properly. But if I update mbed os to 5.13.1 or higher I have an error.

I research this problem and get code which work wrong (commit b272c5f14909705b19397263ec274e45b9e36507):

 struct netif *netif_ = netif_get_by_index(s->conn->pcb.ip->netif_idx);
    if (!netif_) {
        netif_ = &default_interface->netif;
    }
    if (netif_) {
        if ((addr.version == NSAPI_IPv4 && !get_ipv4_addr(netif_)) ||
                (addr.version == NSAPI_IPv6 && !get_ipv6_addr(netif_))) {
            return NSAPI_ERROR_PARAMETER;
        }
    }

Function get_ipv6_addr iterate over all available ipv6 addresses and skip local-link address which is set during network initialization (EMACInterface::connect()->LWIP::Interface::bringup() -> netif_create_ip6_linklocal_address()). Because there is no one other ipv6 address in interface function return NULL. After that return NSAPI_ERROR_PARAMETER occur and socket sendto return error -3003.

target STM32F446ZE on nucleo board
toolchain GCC_ARM 6 2017-q2-update
mbed cli

Issue request type

[ ] Question
[ ] Enhancement
[x] Bug

[ciarmcom]

Internal Jira reference: https://jira.arm.com/browse/MBOCUSTRIA-1729

[0xc0170]

@tymoteuszblochmobica Please review

cc @ARMmbed/mbed-os-ipcore

[tymoteuszblochmobica]

If adress is link local LWIP returns NULL.
const ip_addr_t *LWIP::get_ipv6_addr(const struct netif *netif)
{

if LWIP_IPV6

if (!netif_is_up(netif)) {
    return NULL;
}

for (int i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
    if (ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
            !ip6_addr_islinklocal(netif_ip6_addr(netif, i))) {
        return netif_ip_addr6(netif, i);
    }
}

endif

return NULL;

}

@kjbracey-arm Does ip6_addr_islinklocal have special purpose in this function or can it be removed?

[michalpasztamobica]

@slavaDev503 , the fix is merged, please check if this works fine for you?

[0xc0170]

As we believe this was fixed, we will close. In case there is still an issue, please reopen or create a new bug report if are seeing different issue.