diff --git a/src/basic/in-addr-util.c b/src/basic/in-addr-util.c index bfe855fb4b..d1e457b647 100644 --- a/src/basic/in-addr-util.c +++ b/src/basic/in-addr-util.c @@ -226,6 +226,92 @@ int in_addr_prefix_next(int family, union in_addr_union *u, unsigned prefixlen) return -EAFNOSUPPORT; } +/* + * Calculates the nth prefix of size prefixlen starting from the address denoted by u. + * + * On success 1 will be returned and the calculated prefix will be available in + * u. In the case nth == 0 the input will be left unchanged and 1 will be returned. + * In case the calculation cannot be performed (invalid prefix length, + * overflows would occur) -ERANGE is returned. If the address family given isn't + * supported -EAFNOSUPPORT will be returned. + * + * + * Examples: + * - in_addr_prefix_nth(AF_INET, 192.168.0.0, 24, 2), returns 1, writes 192.168.2.0 to u + * - in_addr_prefix_nth(AF_INET, 192.168.0.0, 24, 0), returns 1, no data written + * - in_addr_prefix_nth(AF_INET, 255.255.255.0, 24, 1), returns -ERANGE, no data written + * - in_addr_prefix_nth(AF_INET, 255.255.255.0, 0, 1), returns -ERANGE, no data written + * - in_addr_prefix_nth(AF_INET6, 2001:db8, 64, 0xff00) returns 1, writes 2001:0db8:0000:ff00:: to u + */ +int in_addr_prefix_nth(int family, union in_addr_union *u, unsigned prefixlen, uint64_t nth) { + assert(u); + + if (prefixlen <= 0) + return -ERANGE; + + if (nth == 0) + return 1; + + if (family == AF_INET) { + uint32_t c, n, t; + if (prefixlen > 32) + prefixlen = 32; + + c = be32toh(u->in.s_addr); + + t = nth << (32 - prefixlen); + + /* Check for wrap */ + if (c > UINT32_MAX - t) + return -ERANGE; + + n = c + t; + + n &= UINT32_C(0xFFFFFFFF) << (32 - prefixlen); + u->in.s_addr = htobe32(n); + return 1; + } + + if (family == AF_INET6) { + struct in6_addr result = {}; + uint8_t overflow = 0; + uint64_t delta; /* this assumes that we only ever have to up to 1<<64 subnets */ + unsigned start_byte = (prefixlen - 1) / 8; + + if (prefixlen > 128) + prefixlen = 128; + + /* First calculate what we have to add */ + delta = nth << ((128 - prefixlen) % 8); + + for (unsigned i = 16; i > 0; i--) { + unsigned j = i - 1; + unsigned d = 0; + + if (j <= start_byte) { + int16_t t; + + d = delta & 0xFF; + delta >>= 8; + + t = u->in6.s6_addr[j] + d + overflow; + overflow = t > UINT8_MAX ? t - UINT8_MAX : 0; + + result.s6_addr[j] = (uint8_t)t; + } else + result.s6_addr[j] = u->in6.s6_addr[j]; + } + + if (overflow || delta != 0) + return -ERANGE; + + u->in6 = result; + return 1; + } + + return -EAFNOSUPPORT; +} + int in_addr_random_prefix( int family, union in_addr_union *u, diff --git a/src/basic/in-addr-util.h b/src/basic/in-addr-util.h index ae2dad0bb1..90d79a5ef5 100644 --- a/src/basic/in-addr-util.h +++ b/src/basic/in-addr-util.h @@ -36,6 +36,7 @@ bool in4_addr_equal(const struct in_addr *a, const struct in_addr *b); int in_addr_equal(int family, const union in_addr_union *a, const union in_addr_union *b); int in_addr_prefix_intersect(int family, const union in_addr_union *a, unsigned aprefixlen, const union in_addr_union *b, unsigned bprefixlen); int in_addr_prefix_next(int family, union in_addr_union *u, unsigned prefixlen); +int in_addr_prefix_nth(int family, union in_addr_union *u, unsigned prefixlen, uint64_t nth); int in_addr_random_prefix(int family, union in_addr_union *u, unsigned prefixlen_fixed_part, unsigned prefixlen); int in_addr_to_string(int family, const union in_addr_union *u, char **ret); int in_addr_prefix_to_string(int family, const union in_addr_union *u, unsigned prefixlen, char **ret); diff --git a/src/test/test-socket-util.c b/src/test/test-socket-util.c index d36caaa71e..d63f212c19 100644 --- a/src/test/test-socket-util.c +++ b/src/test/test-socket-util.c @@ -173,6 +173,45 @@ static void test_in_addr_prefix_next(void) { test_in_addr_prefix_next_one(AF_INET6, "ffff:ffff:ffff:ffff:ffff:ffff:ffff:ff00", 120, NULL); } +static void test_in_addr_prefix_nth_one(unsigned f, const char *before, unsigned pl, uint64_t nth, const char *after) { + union in_addr_union ubefore, uafter, t; + + assert_se(in_addr_from_string(f, before, &ubefore) >= 0); + + t = ubefore; + assert_se((in_addr_prefix_nth(f, &t, pl, nth) > 0) == !!after); + + if (after) { + assert_se(in_addr_from_string(f, after, &uafter) >= 0); + assert_se(in_addr_equal(f, &t, &uafter) > 0); + } +} + +static void test_in_addr_prefix_nth(void) { + log_info("/* %s */", __func__); + + test_in_addr_prefix_nth_one(AF_INET, "192.168.0.0", 24, 0, "192.168.0.0"); + test_in_addr_prefix_nth_one(AF_INET, "192.168.0.0", 24, 1, "192.168.1.0"); + test_in_addr_prefix_nth_one(AF_INET, "192.168.0.0", 24, 4, "192.168.4.0"); + test_in_addr_prefix_nth_one(AF_INET, "192.168.0.0", 25, 1, "192.168.0.128"); + test_in_addr_prefix_nth_one(AF_INET, "192.168.255.0", 25, 1, "192.168.255.128"); + test_in_addr_prefix_nth_one(AF_INET, "192.168.255.0", 24, 0, "192.168.255.0"); + test_in_addr_prefix_nth_one(AF_INET, "255.255.255.255", 32, 1, NULL); + test_in_addr_prefix_nth_one(AF_INET, "255.255.255.255", 0, 1, NULL); + + test_in_addr_prefix_nth_one(AF_INET6, "4400::", 8, 1, "4500::"); + test_in_addr_prefix_nth_one(AF_INET6, "4400::", 7, 1, "4600::"); + test_in_addr_prefix_nth_one(AF_INET6, "4400::", 64, 1, "4400:0:0:1::"); + test_in_addr_prefix_nth_one(AF_INET6, "4400::", 64, 2, "4400:0:0:2::"); + test_in_addr_prefix_nth_one(AF_INET6, "4400::", 64, 0xbad, "4400:0:0:0bad::"); + test_in_addr_prefix_nth_one(AF_INET6, "4400:0:0:ffff::", 64, 1, "4400:0:1::"); + test_in_addr_prefix_nth_one(AF_INET6, "4400::", 56, ((uint64_t)1<<48) -1, "44ff:ffff:ffff:ff00::"); + test_in_addr_prefix_nth_one(AF_INET6, "0000::", 8, 255, "ff00::"); + test_in_addr_prefix_nth_one(AF_INET6, "0000::", 8, 256, NULL); + test_in_addr_prefix_nth_one(AF_INET6, "ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff", 128, 1, NULL); + test_in_addr_prefix_nth_one(AF_INET6, "ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff", 0, 1, NULL); +} + static void test_in_addr_to_string_one(int f, const char *addr) { union in_addr_union ua; _cleanup_free_ char *r = NULL; @@ -673,6 +712,7 @@ int main(int argc, char *argv[]) { test_in_addr_is_null(); test_in_addr_prefix_intersect(); test_in_addr_prefix_next(); + test_in_addr_prefix_nth(); test_in_addr_to_string(); test_in_addr_ifindex_to_string(); test_in_addr_ifindex_from_string_auto();