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I'm trying to set up multiple Apache SSL vhosts, each on a different IPv6 address.

My CentOS7 VPS has a routed /64 IPv6 block assigned to it, let's say 2001:db8:acac:acac::/64, and I can already see packets coming in (tcpdump -nn -i eth0 'ip6 and src or dst net 2001:db8:acac:acac::/64' shows the packets fine).

I am aware I can assign as many individual addresses as I like to eth0 (ip -6 addr add 2001:db8:acac:acac::1234 dev eth0), but I want to get the interface allow apps to bind to any of the 2^64 addresses.

Following advice (see links at bottom), I added a rule (ip -6 rule add from 2001:db8:acac:acac::/64 iif eth0 lookup 200) and a route (ip route add local 2001:db8:acac:acac::/64 dev lo table 200) and now I can ping6 any IP address in the /64 block, and I can connect to services listening on wildcard (e.g. :::22 for ssh) using any address in the /64 block.

The question is: how can I make a program bind to a single address in the /64 block? As no interface owns any of the addresses in the block, I see the following in the apache logs:

... AH00072: make_sock: could not bind to address [2001:db8:acac:acac::1234]:443

I have seen mentions of IP_TRANSPARENT as a possible solution, but cannot find this mentioned in Apache source, only in bits/in.h, included by netinet/in.h.

Has anyone got this to work, either for Apache or for other apps (in particular: dovecot, postfix, bind)?

Relevant articles read before posting this question:

kasperd
  • 31,086
Ashley GC
  • 31

2 Answers2

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You can assign that address to absolutely any interface. For example, assign it to lo (in addition to ::1). IPv6 is pretty good at having multiple addresses on any interface. Then, after you made the address local, you can listen on it.

UPD: As I see, this idea doesn't differ much from that of mentioned in your first link about assigning address block to lo. Essentially this is the same, but block is degenerate to a single address.

Nikita Kipriyanov
  • 15,624
0

While I have not yet been able to make apache bind to a single address which is not owned by an interface, I have made a test C program which works, and can bind to any IPv6 address, regardless of whether the address is owned by an interface:

/*
  Test program to bind to an IPv6 address not owned by an interface.
  This code is from public domain sources, and is released into the public domain.
*/

#include <arpa/inet.h>
#include <error.h>
#include <errno.h>
#include <net/if.h>
#include <netinet/in.h> // also includes bits/in.h
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h> // also includes bits/ioctls.h
#include <sys/socket.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>

// A real address to use as a sanity check and make sure the program can 
// bind to an address which *is* owned by an interface
#define REALADDR {{{0x2a,0x00, ...}}}

// A fake address to show the program can bind to an address which is *not* 
// owned by any interface
#define SOMEADDR {{{0x20,0x01, 0x0d,0xb8, 0x00,0x00, 0x00,0x00, \
                    0x00,0x00, 0x00,0x00, 0x00,0x00, 0x00,0x01 }}}

int main(int argc, char *argv[])
{
    struct sockaddr_in6 serv_addr;
    int listenfd = 0, connfd = 0, i;

    char sendBuff[1025];
    time_t ticks;

    listenfd = socket(AF_INET6, SOCK_STREAM, 0);
    printf("socket fd is %d\n", listenfd);
    memset(&serv_addr, 0, sizeof(serv_addr));
    memset(sendBuff, 0, sizeof(sendBuff));

    serv_addr.sin6_family = AF_INET6;
    serv_addr.sin6_port = htons(5000);
    struct in6_addr someaddr = SOMEADDR;
    serv_addr.sin6_addr = someaddr;

    // Here's the magic:
    int opt = 1;
    if (setsockopt(listenfd, SOL_IP, IP_FREEBIND, &opt, sizeof(opt)) < 0)
        error(1, errno, "setsockopt(IP_FREEBIND) failed");

    printf("Binding to ");
    for (i = 0; i < 14; i += 2)
        printf("%x:", (serv_addr.sin6_addr.s6_addr[i] << 8) + 
            serv_addr.sin6_addr.s6_addr[i+1]);
    printf("%x\n", (serv_addr.sin6_addr.s6_addr[14] << 8) + 
        serv_addr.sin6_addr.s6_addr[15]);
    if (bind(listenfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0)
        error(1, errno, "bind failed");

    if (listen(listenfd, 10) < 0)
        error(1, errno, "listen failed");

    while(1)
    {
        connfd = accept(listenfd, (struct sockaddr*)NULL, NULL);
        printf("accept returned %d\n", connfd);

        // Send some data - the current date and time.
        ticks = time(NULL);
        snprintf(sendBuff, sizeof(sendBuff), "Now is %.24s\r\n", ctime(&ticks));
        write(connfd, sendBuff, strlen(sendBuff));

        close(connfd);
        sleep(1);
     }
}
Ashley GC
  • 31