inet_addr_local.c

[詳解]

/*++
/* NAME
/*  inet_addr_local 3
/* SUMMARY
/*  determine if IP address is local
/* SYNOPSIS
/*  #include <inet_addr_local.h>
/*
/*  int inet_addr_local(addr_list, mask_list, addr_family_list)
/*  INET_ADDR_LIST *addr_list;
/*  INET_ADDR_LIST *mask_list;
/*  unsigned *addr_family;
/* DESCRIPTION
/*  inet_addr_local() determines all active IP interface addresses
/*  of the local system. Any address found is appended to the
/*  specified address list. The result value is the number of
/*  active interfaces found.
/*
/*  The mask_list is either a null pointer, or it is a list that
/*  receives the netmasks of the interface addresses that were found.
/*
/*  The addr_family_list specifies one or more of AF_INET or AF_INET6.
/* DIAGNOSTICS
/*  Fatal errors: out of memory.
/* SEE ALSO
/*  inet_addr_list(3) address list management
/* LICENSE
/* .ad
/* .fi
/*  The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*  Wietse Venema
/*  IBM T.J. Watson Research
/*  P.O. Box 704
/*  Yorktown Heights, NY 10598, USA
/*
/*  Dean C. Strik
/*  Department ICT
/*  Eindhoven University of Technology
/*  P.O. Box 513
/*  5600 MB  Eindhoven, Netherlands
/*  E-mail: <dean@ipnet6.org>
/*--*/

/* System library. */

#include <sys_defs.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <arpa/inet.h>
#include <unistd.h>
#ifdef USE_SYS_SOCKIO_H
#include <sys/sockio.h>
#endif
#include <errno.h>
#include <string.h>
#ifdef HAS_IPV6             /* Linux only? */
#include <netdb.h>
#include <stdio.h>
#endif
#ifdef HAVE_GETIFADDRS
#include <ifaddrs.h>
#endif

/* Utility library. */

#include <msg.h>
#include <mymalloc.h>
#include <vstring.h>
#include <inet_addr_list.h>
#include <inet_addr_local.h>
#include <myaddrinfo.h>
#include <sock_addr.h>
#include <mask_addr.h>
#include <hex_code.h>

 /*
  * Postfix needs its own interface address information to determine whether
  * or not it is an MX host for some destination; without this information,
  * mail would loop between MX hosts. Postfix also needs its interface
  * addresses to figure out whether or not it is final destination for
  * addresses of the form username@[ipaddress].
  * 
  * Postfix needs its own interface netmask information when no explicit
  * mynetworks setting is given in main.cf, and "mynetworks_style = subnet".
  * The mynetworks parameter controls, among others, what mail clients are
  * allowed to relay mail through Postfix.
  * 
  * Different systems have different ways to find out this information. We will
  * therefore use OS dependent methods. An overview:
  * 
  * - Use getifaddrs() when available.  This supports both IPv4/IPv6 addresses.
  * The implementation however is not present in all major operating systems.
  * 
  * - Use SIOCGLIFCONF when available. This supports both IPv4/IPv6 addresses.
  * With SIOCGLIFNETMASK we can obtain the netmask for either address family.
  * Again, this is not present in all major operating systems.
  * 
  * - On Linux, glibc's getifaddrs(3) has returned IPv4 information for some
  * time, but IPv6 information was not returned until 2.3.3. With older Linux
  * versions we get IPv4 interface information with SIOCGIFCONF, and read
  * IPv6 address/prefix information from a file in the /proc filesystem.
  * 
  * - On other systems we expect SIOCGIFCONF to return IPv6 addresses. Since
  * SIOCGIFNETMASK does not work reliably for IPv6 addresses, we always set
  * the prefix length to /128 (host), and expect the user to configure a more
  * appropriate mynetworks setting if needed.
  * 
  * XXX: Each lookup method is implemented by its own function, so we duplicate
  * some code. In this case, I think this is better than really drowning in
  * the #ifdefs...
  * 
  * -- Dean Strik (dcs)
  */

#ifndef HAVE_GETIFADDRS

/* ial_socket - make socket for ioctl() operations */

static int ial_socket(int af)
{
    const char *myname = "inet_addr_local[socket]";
    int     sock;

    /*
     * The host may not be actually configured with IPv6. When IPv6 support
     * is not actually in the kernel, don't consider failure to create an
     * IPv6 socket as fatal. This could be tuned better though. For other
     * families, the error is fatal.
     * 
     * XXX Now that Postfix controls protocol support centrally with the
     * inet_proto(3) module, this workaround should no longer be needed.
     */
    if ((sock = socket(af, SOCK_DGRAM, 0)) < 0) {
#ifdef HAS_IPV6
    if (af == AF_INET6) {
        if (msg_verbose)
        msg_warn("%s: socket: %m", myname);
        return (-1);
    }
#endif
    msg_fatal("%s: socket: %m", myname);
    }
    return (sock);
}

#endif

#ifdef HAVE_GETIFADDRS

/*
 * The getifaddrs(3) function, introduced by BSD/OS, provides a
 * platform-independent way of requesting interface addresses,
 * including IPv6 addresses. The implementation however is not
 * present in all major operating systems.
 */

/* ial_getifaddrs - determine IP addresses using getifaddrs(3) */

static int ial_getifaddrs(INET_ADDR_LIST *addr_list,
                      INET_ADDR_LIST *mask_list,
                      int af)
{
    const char *myname = "inet_addr_local[getifaddrs]";
    struct ifaddrs *ifap, *ifa;
    struct sockaddr *sa, *sam;

    if (getifaddrs(&ifap) < 0)
    msg_fatal("%s: getifaddrs: %m", myname);

    /*
     * Get the address of each IP network interface. According to BIND we
     * must include interfaces that are down because the machine may still
     * receive packets for that address (yes, via some other interface).
     * Having no way to verify this claim on every machine, I will give them
     * the benefit of the doubt.
     * 
     * FIX 200501: The IPv6 patch did not report NetBSD loopback interfaces;
     * fixed by replacing IFF_RUNNING by IFF_UP.
     * 
     * FIX 200501: The IPV6 patch did not skip wild-card interface addresses
     * (tested on FreeBSD).
     */
    for (ifa = ifap; ifa; ifa = ifa->ifa_next) {
    if (!(ifa->ifa_flags & IFF_UP) || ifa->ifa_addr == 0)
        continue;
    sa = ifa->ifa_addr;
    if (af != AF_UNSPEC && sa->sa_family != af)
        continue;
    sam = ifa->ifa_netmask;
    if (sam == 0) {
        /* XXX In mynetworks, a null netmask would match everyone. */
        msg_warn("ignoring interface with null netmask, address family %d",
             sa->sa_family);
        continue;
    }
    switch (sa->sa_family) {
    case AF_INET:
        if (SOCK_ADDR_IN_ADDR(sa).s_addr == INADDR_ANY)
        continue;
        break;
#ifdef HAS_IPV6
    case AF_INET6:
        if (IN6_IS_ADDR_UNSPECIFIED(&SOCK_ADDR_IN6_ADDR(sa)))
        continue;
        break;
#endif
    default:
        continue;
    }

    inet_addr_list_append(addr_list, sa);
    if (mask_list != 0) {

        /*
         * Unfortunately, sa_len/sa_family may be broken in the netmask
         * sockaddr structure. We must fix this manually to have correct
         * addresses.   --dcs
         */
#ifdef HAS_SA_LEN
        sam->sa_len = sa->sa_family == AF_INET6 ?
        sizeof(struct sockaddr_in6) :
        sizeof(struct sockaddr_in);
#endif
        sam->sa_family = sa->sa_family;
        inet_addr_list_append(mask_list, sam);
    }
    }
    freeifaddrs(ifap);
    return (0);
}

#elif defined(HAS_SIOCGLIF)     /* HAVE_GETIFADDRS */

/*
 * The SIOCLIF* ioctls are the successors of SIOCGIF* on the Solaris
 * and HP/UX operating systems. The data is stored in sockaddr_storage
 * structure. Both IPv4 and IPv6 addresses are returned though these
 * calls.
 */
#define NEXT_INTERFACE(lifr)    (lifr + 1)
#define LIFREQ_SIZE(lifr)   sizeof(lifr[0])

/* ial_siocglif - determine IP addresses using ioctl(SIOCGLIF*) */

static int ial_siocglif(INET_ADDR_LIST *addr_list,
                    INET_ADDR_LIST *mask_list,
                    int af)
{
    const char *myname = "inet_addr_local[siocglif]";
    struct lifconf lifc;
    struct lifreq *lifr;
    struct lifreq *lifr_mask;
    struct lifreq *the_end;
    struct sockaddr *sa;
    int     sock;
    VSTRING *buf;

    /*
     * See also comments in ial_siocgif()
     */
    if (af != AF_INET && af != AF_INET6)
    msg_fatal("%s: address family was %d, must be AF_INET (%d) or "
          "AF_INET6 (%d)", myname, af, AF_INET, AF_INET6);
    sock = ial_socket(af);
    if (sock < 0)
    return (0);
    buf = vstring_alloc(1024);
    for (;;) {
    memset(&lifc, 0, sizeof(lifc));
    lifc.lifc_family = AF_UNSPEC;       /* XXX Why??? */
    lifc.lifc_len = vstring_avail(buf);
    lifc.lifc_buf = vstring_str(buf);
    if (ioctl(sock, SIOCGLIFCONF, (char *) &lifc) < 0) {
        if (errno != EINVAL)
        msg_fatal("%s: ioctl SIOCGLIFCONF: %m", myname);
    } else if (lifc.lifc_len < vstring_avail(buf) / 2)
        break;
    VSTRING_SPACE(buf, vstring_avail(buf) * 2);
    }

    the_end = (struct lifreq *) (lifc.lifc_buf + lifc.lifc_len);
    for (lifr = lifc.lifc_req; lifr < the_end;) {
    sa = (struct sockaddr *) &lifr->lifr_addr;
    if (sa->sa_family != af) {
        lifr = NEXT_INTERFACE(lifr);
        continue;
    }
    if (af == AF_INET) {
        if (SOCK_ADDR_IN_ADDR(sa).s_addr == INADDR_ANY) {
        lifr = NEXT_INTERFACE(lifr);
        continue;
        }
#ifdef HAS_IPV6
    } else if (af == AF_INET6) {
        if (IN6_IS_ADDR_UNSPECIFIED(&SOCK_ADDR_IN6_ADDR(sa))) {
        lifr = NEXT_INTERFACE(lifr);
        continue;
        }
    }
#endif
    inet_addr_list_append(addr_list, sa);
    if (mask_list) {
        lifr_mask = (struct lifreq *) mymalloc(sizeof(struct lifreq));
        memcpy((void *) lifr_mask, (void *) lifr, sizeof(struct lifreq));
        if (ioctl(sock, SIOCGLIFNETMASK, lifr_mask) < 0)
        msg_fatal("%s: ioctl(SIOCGLIFNETMASK): %m", myname);
        /* XXX: Check whether sa_len/family are honoured --dcs */
        inet_addr_list_append(mask_list,
                  (struct sockaddr *) &lifr_mask->lifr_addr);
        myfree((void *) lifr_mask);
    }
    lifr = NEXT_INTERFACE(lifr);
    }
    vstring_free(buf);
    (void) close(sock);
    return (0);
}

#else                   /* HAVE_SIOCGLIF */

/*
 * The classic SIOCGIF* ioctls. Modern BSD operating systems will
 * also return IPv6 addresses through these structure. Note however
 * that recent versions of these operating systems have getifaddrs.
 */
#if defined(_SIZEOF_ADDR_IFREQ)
#define NEXT_INTERFACE(ifr) ((struct ifreq *) \
    ((char *) ifr + _SIZEOF_ADDR_IFREQ(*ifr)))
#define IFREQ_SIZE(ifr) _SIZEOF_ADDR_IFREQ(*ifr)
#elif defined(HAS_SA_LEN)
#define NEXT_INTERFACE(ifr) ((struct ifreq *) \
    ((char *) ifr + sizeof(ifr->ifr_name) + ifr->ifr_addr.sa_len))
#define IFREQ_SIZE(ifr) (sizeof(ifr->ifr_name) + ifr->ifr_addr.sa_len)
#else
#define NEXT_INTERFACE(ifr) (ifr + 1)
#define IFREQ_SIZE(ifr) sizeof(ifr[0])
#endif

/* ial_siocgif - determine IP addresses using ioctl(SIOCGIF*) */

static int ial_siocgif(INET_ADDR_LIST *addr_list,
                       INET_ADDR_LIST *mask_list,
                       int af)
{
    const char *myname = "inet_addr_local[siocgif]";
    struct in_addr addr;
    struct ifconf ifc;
    struct ifreq *ifr;
    struct ifreq *ifr_mask;
    struct ifreq *the_end;
    int     sock;
    VSTRING *buf;

    /*
     * Get the network interface list. XXX The socket API appears to have no
     * function that returns the number of network interfaces, so we have to
     * guess how much space is needed to store the result.
     * 
     * On BSD-derived systems, ioctl SIOCGIFCONF returns as much information as
     * possible, leaving it up to the application to repeat the request with
     * a larger buffer if the result caused a tight fit.
     * 
     * Other systems, such as Solaris 2.5, generate an EINVAL error when the
     * buffer is too small for the entire result. Workaround: ignore EINVAL
     * errors and repeat the request with a larger buffer. The downside is
     * that the program can run out of memory due to a non-memory problem,
     * making it more difficult than necessary to diagnose the real problem.
     */
    sock = ial_socket(af);
    if (sock < 0)
    return (0);
    buf = vstring_alloc(1024);
    for (;;) {
    ifc.ifc_len = vstring_avail(buf);
    ifc.ifc_buf = vstring_str(buf);
    if (ioctl(sock, SIOCGIFCONF, (char *) &ifc) < 0) {
        if (errno != EINVAL)
        msg_fatal("%s: ioctl SIOCGIFCONF: %m", myname);
    } else if (ifc.ifc_len < vstring_avail(buf) / 2)
        break;
    VSTRING_SPACE(buf, vstring_avail(buf) * 2);
    }

    the_end = (struct ifreq *) (ifc.ifc_buf + ifc.ifc_len);
    for (ifr = ifc.ifc_req; ifr < the_end;) {
    if (ifr->ifr_addr.sa_family != af) {
        ifr = NEXT_INTERFACE(ifr);
        continue;
    }
    if (af == AF_INET) {
        addr = ((struct sockaddr_in *) & ifr->ifr_addr)->sin_addr;
        if (addr.s_addr != INADDR_ANY) {
        inet_addr_list_append(addr_list, &ifr->ifr_addr);
        if (mask_list) {
            ifr_mask = (struct ifreq *) mymalloc(IFREQ_SIZE(ifr));
            memcpy((void *) ifr_mask, (void *) ifr, IFREQ_SIZE(ifr));
            if (ioctl(sock, SIOCGIFNETMASK, ifr_mask) < 0)
            msg_fatal("%s: ioctl SIOCGIFNETMASK: %m", myname);

            /*
             * Note that this SIOCGIFNETMASK has truly screwed up the
             * contents of sa_len/sa_family. We must fix this
             * manually to have correct addresses.   --dcs
             */
            ifr_mask->ifr_addr.sa_family = af;
#ifdef HAS_SA_LEN
            ifr_mask->ifr_addr.sa_len = sizeof(struct sockaddr_in);
#endif
            inet_addr_list_append(mask_list, &ifr_mask->ifr_addr);
            myfree((void *) ifr_mask);
        }
        }
    }
#ifdef HAS_IPV6
    else if (af == AF_INET6) {
        struct sockaddr *sa;

        sa = SOCK_ADDR_PTR(&ifr->ifr_addr);
        if (!(IN6_IS_ADDR_UNSPECIFIED(&SOCK_ADDR_IN6_ADDR(sa)))) {
        inet_addr_list_append(addr_list, sa);
        if (mask_list) {
            /* XXX Assume /128 for everything */
            struct sockaddr_in6 mask6;

            mask6 = *SOCK_ADDR_IN6_PTR(sa);
            memset((void *) &mask6.sin6_addr, ~0,
               sizeof(mask6.sin6_addr));
            inet_addr_list_append(mask_list, SOCK_ADDR_PTR(&mask6));
        }
        }
    }
#endif
    ifr = NEXT_INTERFACE(ifr);
    }
    vstring_free(buf);
    (void) close(sock);
    return (0);
}

#endif                  /* HAVE_SIOCGLIF */

#ifdef HAS_PROCNET_IFINET6

/*
 * Older Linux versions lack proper calls to retrieve IPv6 interface
 * addresses. Instead, the addresses can be read from a file in the
 * /proc tree. The most important issue with this approach however
 * is that the /proc tree may not always be available, for example
 * in a chrooted environment or in "hardened" (sic) installations.
 */

/* ial_procnet_ifinet6 - determine IPv6 addresses using /proc/net/if_inet6 */

static int ial_procnet_ifinet6(INET_ADDR_LIST *addr_list,
                           INET_ADDR_LIST *mask_list)
{
    const char *myname = "inet_addr_local[procnet_ifinet6]";
    FILE   *fp;
    char    buf[BUFSIZ];
    unsigned plen;
    VSTRING *addrbuf;
    struct sockaddr_in6 addr;
    struct sockaddr_in6 mask;

    /*
     * Example: 00000000000000000000000000000001 01 80 10 80 lo
     * 
     * Fields: address, interface index, prefix length, scope value
     * (net/ipv6.h), interface flags (linux/rtnetlink.h), device name.
     * 
     * FIX 200501 The IPv6 patch used fscanf(), which will hang on unexpected
     * input. Use fgets() + sscanf() instead.
     */
    if ((fp = fopen(_PATH_PROCNET_IFINET6, "r")) != 0) {
    addrbuf = vstring_alloc(MAI_V6ADDR_BYTES + 1);
    memset((void *) &addr, 0, sizeof(addr));
    addr.sin6_family = AF_INET6;
#ifdef HAS_SA_LEN
    addr.sin6_len = sizeof(addr);
#endif
    mask = addr;
    while (fgets(buf, sizeof(buf), fp) != 0) {
        /* 200501 hex_decode() is light-weight compared to getaddrinfo(). */
        if (hex_decode(addrbuf, buf, MAI_V6ADDR_BYTES * 2) == 0
        || sscanf(buf + MAI_V6ADDR_BYTES * 2, " %*x %x", &plen) != 1
        || plen > MAI_V6ADDR_BITS) {
        msg_warn("unexpected data in %s - skipping IPv6 configuration",
             _PATH_PROCNET_IFINET6);
        break;
        }
        /* vstring_str(addrbuf) has worst-case alignment. */
        addr.sin6_addr = *(struct in6_addr *) vstring_str(addrbuf);
        inet_addr_list_append(addr_list, SOCK_ADDR_PTR(&addr));

        memset((void *) &mask.sin6_addr, ~0, sizeof(mask.sin6_addr));
        mask_addr((unsigned char *) &mask.sin6_addr,
              sizeof(mask.sin6_addr), plen);
        inet_addr_list_append(mask_list, SOCK_ADDR_PTR(&mask));
    }
    vstring_free(addrbuf);
    fclose(fp);             /* FIX 200501 */
    } else {
    msg_warn("can't open %s (%m) - skipping IPv6 configuration",
         _PATH_PROCNET_IFINET6);
    }
    return (0);
}

#endif                  /* HAS_PROCNET_IFINET6 */

/* inet_addr_local - find all IP addresses for this host */

int     inet_addr_local(INET_ADDR_LIST *addr_list, INET_ADDR_LIST *mask_list,
                    unsigned *addr_family_list)
{
    const char *myname = "inet_addr_local";
    int     initial_count = addr_list->used;
    unsigned family;
    int     count;

    while ((family = *addr_family_list++) != 0) {

    /*
     * IP Version 4
     */
    if (family == AF_INET) {
        count = addr_list->used;
#if defined(HAVE_GETIFADDRS)
        ial_getifaddrs(addr_list, mask_list, AF_INET);
#elif defined (HAS_SIOCGLIF)
        ial_siocglif(addr_list, mask_list, AF_INET);
#else
        ial_siocgif(addr_list, mask_list, AF_INET);
#endif
        if (msg_verbose)
        msg_info("%s: configured %d IPv4 addresses",
             myname, addr_list->used - count);
    }

    /*
     * IP Version 6
     */
#ifdef HAS_IPV6
    else if (family == AF_INET6) {
        count = addr_list->used;
#if defined(HAVE_GETIFADDRS)
        ial_getifaddrs(addr_list, mask_list, AF_INET6);
#elif defined(HAS_PROCNET_IFINET6)
        ial_procnet_ifinet6(addr_list, mask_list);
#elif defined(HAS_SIOCGLIF)
        ial_siocglif(addr_list, mask_list, AF_INET6);
#else
        ial_siocgif(addr_list, mask_list, AF_INET6);
#endif
        if (msg_verbose)
        msg_info("%s: configured %d IPv6 addresses", myname,
             addr_list->used - count);
    }
#endif

    /*
     * Something's not right.
     */
    else
        msg_panic("%s: unknown address family %d", myname, family);
    }
    return (addr_list->used - initial_count);
}

#ifdef TEST

#include <string.h>
#include <vstream.h>
#include <msg_vstream.h>
#include <inet_proto.h>

int     main(int unused_argc, char **argv)
{
    INET_ADDR_LIST addr_list;
    INET_ADDR_LIST mask_list;
    MAI_HOSTADDR_STR hostaddr;
    MAI_HOSTADDR_STR hostmask;
    struct sockaddr *sa;
    int     i;
    INET_PROTO_INFO *proto_info;

    msg_vstream_init(argv[0], VSTREAM_ERR);
    msg_verbose = 1;

    proto_info = inet_proto_init(argv[0],
                 argv[1] ? argv[1] : INET_PROTO_NAME_ALL);
    inet_addr_list_init(&addr_list);
    inet_addr_list_init(&mask_list);
    inet_addr_local(&addr_list, &mask_list, proto_info->ai_family_list);

    if (addr_list.used == 0)
    msg_fatal("cannot find any active network interfaces");

    if (addr_list.used == 1)
    msg_warn("found only one active network interface");

    for (i = 0; i < addr_list.used; i++) {
    sa = SOCK_ADDR_PTR(addr_list.addrs + i);
    SOCKADDR_TO_HOSTADDR(SOCK_ADDR_PTR(sa), SOCK_ADDR_LEN(sa),
                 &hostaddr, (MAI_SERVPORT_STR *) 0, 0);
    sa = SOCK_ADDR_PTR(mask_list.addrs + i);
    SOCKADDR_TO_HOSTADDR(SOCK_ADDR_PTR(sa), SOCK_ADDR_LEN(sa),
                 &hostmask, (MAI_SERVPORT_STR *) 0, 0);
    vstream_printf("%s/%s\n", hostaddr.buf, hostmask.buf);
    vstream_fflush(VSTREAM_OUT);
    }
    inet_addr_list_free(&addr_list);
    inet_addr_list_free(&mask_list);
    return (0);
}

#endif