src/shared/in-addr-util.c

/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  This file is part of systemd.

  Copyright 2014 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <arpa/inet.h>

#include "in-addr-util.h"

int in_addr_is_null(int family, const union in_addr_union *u) {
        assert(u);

        if (family == AF_INET)
                return u->in.s_addr == 0;

        if (family == AF_INET6)
                return
                        u->in6.s6_addr32[0] == 0 &&
                        u->in6.s6_addr32[1] == 0 &&
                        u->in6.s6_addr32[2] == 0 &&
                        u->in6.s6_addr32[3] == 0;

        return -EAFNOSUPPORT;
}

int in_addr_is_link_local(int family, const union in_addr_union *u) {
        assert(u);

        if (family == AF_INET)
                return (be32toh(u->in.s_addr) & 0xFFFF0000) == (169U << 24 | 254U << 16);

        if (family == AF_INET6)
                return IN6_IS_ADDR_LINKLOCAL(&u->in6);

        return -EAFNOSUPPORT;
}

int in_addr_equal(int family, const union in_addr_union *a, const union in_addr_union *b) {
        assert(a);
        assert(b);

        if (family == AF_INET)
                return a->in.s_addr == b->in.s_addr;

        if (family == AF_INET6)
                return
                        a->in6.s6_addr32[0] == b->in6.s6_addr32[0] &&
                        a->in6.s6_addr32[1] == b->in6.s6_addr32[1] &&
                        a->in6.s6_addr32[2] == b->in6.s6_addr32[2] &&
                        a->in6.s6_addr32[3] == b->in6.s6_addr32[3];

        return -EAFNOSUPPORT;
}

int in_addr_prefix_intersect(
                int family,
                const union in_addr_union *a,
                unsigned aprefixlen,
                const union in_addr_union *b,
                unsigned bprefixlen) {

        unsigned m;

        assert(a);
        assert(b);

        /* Checks whether there are any addresses that are in both
         * networks */

        m = MIN(aprefixlen, bprefixlen);

        if (family == AF_INET) {
                uint32_t x, nm;

                x = be32toh(a->in.s_addr ^ b->in.s_addr);
                nm = (m == 0) ? 0 : 0xFFFFFFFFUL << (32 - m);

                return (x & nm) == 0;
        }

        if (family == AF_INET6) {
                unsigned i;

                if (m > 128)
                        m = 128;

                for (i = 0; i < 16; i++) {
                        uint8_t x, nm;

                        x = a->in6.s6_addr[i] ^ b->in6.s6_addr[i];

                        if (m < 8)
                                nm = 0xFF << (8 - m);
                        else
                                nm = 0xFF;

                        if ((x & nm) != 0)
                                return 0;

                        if (m > 8)
                                m -= 8;
                        else
                                m = 0;
                }

                return 1;
        }

        return -EAFNOSUPPORT;
}

int in_addr_prefix_next(int family, union in_addr_union *u, unsigned prefixlen) {
        assert(u);

        /* Increases the network part of an address by one. Returns
         * positive it that succeeds, or 0 if this overflows. */

        if (prefixlen <= 0)
                return 0;

        if (family == AF_INET) {
                uint32_t c, n;

                if (prefixlen > 32)
                        prefixlen = 32;

                c = be32toh(u->in.s_addr);
                n = c + (1UL << (32 - prefixlen));
                if (n < c)
                        return 0;
                n &= 0xFFFFFFFFUL << (32 - prefixlen);

                u->in.s_addr = htobe32(n);
                return 1;
        }

        if (family == AF_INET6) {
                struct in6_addr add = {}, result;
                uint8_t overflow = 0;
                unsigned i;

                if (prefixlen > 128)
                        prefixlen = 128;

                /* First calculate what we have to add */
                add.s6_addr[(prefixlen-1) / 8] = 1 << (7 - (prefixlen-1) % 8);

                for (i = 16; i > 0; i--) {
                        unsigned j = i - 1;

                        result.s6_addr[j] = u->in6.s6_addr[j] + add.s6_addr[j] + overflow;
                        overflow = (result.s6_addr[j] < u->in6.s6_addr[j]);
                }

                if (overflow)
                        return 0;

                u->in6 = result;
                return 1;
        }

        return -EAFNOSUPPORT;
}

int in_addr_to_string(int family, const union in_addr_union *u, char **ret) {
        char *x;
        size_t l;

        assert(u);
        assert(ret);

        if (family == AF_INET)
                l = INET_ADDRSTRLEN;
        else if (family == AF_INET6)
                l = INET6_ADDRSTRLEN;
        else
                return -EAFNOSUPPORT;

        x = new(char, l);
        if (!x)
                return -ENOMEM;

        errno = 0;
        if (!inet_ntop(family, u, x, l)) {
                free(x);
                return errno ? -errno : -EINVAL;
        }

        *ret = x;
        return 0;
}

int in_addr_from_string(int family, const char *s, union in_addr_union *ret) {

        assert(s);
        assert(ret);

        if (!IN_SET(family, AF_INET, AF_INET6))
                return -EAFNOSUPPORT;

        errno = 0;
        if (inet_pton(family, s, ret) <= 0)
                return errno ? -errno : -EINVAL;

        return 0;
}

int in_addr_from_string_auto(const char *s, int *family, union in_addr_union *ret) {
        int r;

        assert(s);
        assert(family);
        assert(ret);

        r = in_addr_from_string(AF_INET, s, ret);
        if (r >= 0) {
                *family = AF_INET;
                return 0;
        }

        r = in_addr_from_string(AF_INET6, s, ret);
        if (r >= 0) {
                *family = AF_INET6;
                return 0;
        }

        return -EINVAL;
}

unsigned in_addr_netmask_to_prefixlen(const struct in_addr *addr) {
        assert(addr);

        return 32 - u32ctz(be32toh(addr->s_addr));
}

int in_addr_default_prefixlen(const struct in_addr *addr, unsigned char *prefixlen) {
        uint8_t msb_octet = *(uint8_t*) addr;

        /* addr may not be aligned, so make sure we only access it byte-wise */

        assert(addr);
        assert(prefixlen);

        if (msb_octet < 128)
                /* class A, leading bits: 0 */
                *prefixlen = 8;
        else if (msb_octet < 192)
                /* class B, leading bits 10 */
                *prefixlen = 16;
        else if (msb_octet < 224)
                /* class C, leading bits 110 */
                *prefixlen = 24;
        else
                /* class D or E, no default prefixlen */
                return -ERANGE;

        return 0;
}

int in_addr_default_subnet_mask(const struct in_addr *addr, struct in_addr *mask) {
        unsigned char prefixlen;
        int r;

        assert(addr);
        assert(mask);

        r = in_addr_default_prefixlen(addr, &prefixlen);
        if (r < 0)
                return r;

        assert(prefixlen > 0 && prefixlen < 32);

        mask->s_addr = htobe32((0xffffffff << (32 - prefixlen)) & 0xffffffff);

        return 0;
}