JOIN_ANYCAST breakage w. "net: ipv6: put host and anycast routes on device with address"

[Florian Westphal]

Hi David

This test program no longer works with 4.14
(recvfrom: Resource temporarily unavailable)

after reverting commit
4832c30d5458387ff2533ff66fbde26ad8bb5a2d
(net: ipv6: put host and anycast routes on device with address)

it will work again ("OK").

Could you please have a look at this?

Thanks!
----------------------
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <string.h>
#include <netinet/in.h>
#include <errno.h>
#include <sys/ioctl.h>

#include <unistd.h>
#include <stdint.h>

#define ADDR    "fe80::1"
#define MAGIC   0x1c3c01a

int main(int argc, char *argv[])
{
        struct ipv6_mreq nreq = {};
        struct sockaddr_in6 addr = {
                .sin6_family = AF_INET6,
                .sin6_port = htons(12345),
        };
        int fd, fd2, index, tmp;

        if (argc < 2)
                return 1;

        fd = socket(AF_INET6, SOCK_DGRAM, 0);
        fd2 = socket(AF_INET6, SOCK_DGRAM, 0);
        if (fd < 0 || fd2 < 0) {
                perror("socket");
                return 1;
        }
        index = if_nametoindex(argv[1]);
        if (index <= 0) {
                perror("if_nametoindex");
                return 1;
        }

        nreq.ipv6mr_interface = index;
        inet_pton(AF_INET6, ADDR, &nreq.ipv6mr_multiaddr);
        if (setsockopt(fd, IPPROTO_IPV6, IPV6_JOIN_ANYCAST,
            &nreq, sizeof(nreq)) < 0) {
                perror("setsockopt");
                return 1;
        }

        addr.sin6_addr = in6addr_any;
        if (bind(fd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
                perror("bind");
                return 1;
        }

        addr.sin6_port = htons(12346);
        inet_pton(AF_INET6, "::", &addr.sin6_addr);
        if (bind(fd2, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
                perror("bind");
                return 1;
        }

        inet_pton(AF_INET6, ADDR, &addr.sin6_addr);
        addr.sin6_port = htons(12345);
        tmp = MAGIC;
        if (sendto(fd2, &tmp, sizeof(tmp), 0,
                        (struct sockaddr *)&addr, sizeof(addr)) < 0) {
                perror("sendto");
                return 1;
        }

        if (recvfrom(fd, (void *)&tmp, sizeof(tmp), MSG_DONTWAIT,
                                NULL, NULL) < 0) {
                perror("recvfrom");
                return 1;
        }

        if (tmp != MAGIC)
                return 111;

        puts("OK");
        return 0;
}