From 9164338b2e6943ded69f623f2c39a46cb94d35dd Mon Sep 17 00:00:00 2001 From: Yu Watanabe Date: Wed, 17 Feb 2021 20:01:26 +0900 Subject: [PATCH] in-addr-util: make in_addr_prefix_nth() always return valid prefix Previously, e.g. in_addr_prefix_nth(2400::1, prefixlen=32, nth=1) does not return 2400:1:: but does 2400:1::1. --- src/basic/in-addr-util.c | 43 +++++++++++++++--------------------- src/test/test-in-addr-util.c | 13 ++++++----- 2 files changed, 26 insertions(+), 30 deletions(-) diff --git a/src/basic/in-addr-util.c b/src/basic/in-addr-util.c index 343f62c5dc1..aa681b7bb79 100644 --- a/src/basic/in-addr-util.c +++ b/src/basic/in-addr-util.c @@ -199,8 +199,7 @@ int in_addr_prefix_next(int family, union in_addr_union *u, unsigned prefixlen) * Calculates the nth prefix of size prefixlen starting from the address denoted by u. * * On success 0 will be returned and the calculated prefix will be available in - * u. In the case nth == 0 the input will be left unchanged and 0 will be returned. - * In case the calculation cannot be performed (invalid prefix length, + * u. 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. * @@ -217,9 +216,6 @@ int in_addr_prefix_nth(int family, union in_addr_union *u, unsigned prefixlen, u if (prefixlen <= 0) return -ERANGE; - if (nth == 0) - return 0; - if (family == AF_INET) { uint32_t c, n, t; @@ -242,38 +238,35 @@ int in_addr_prefix_nth(int family, union in_addr_union *u, unsigned prefixlen, u } 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; + bool overflow = false; if (prefixlen > 128) return -ERANGE; - /* First calculate what we have to add */ - delta = nth << ((128 - prefixlen) % 8); - for (unsigned i = 16; i > 0; i--) { - unsigned j = i - 1; + unsigned t, j = i - 1, p = j * 8; - if (j <= start_byte) { - unsigned t, d; + if (p >= prefixlen) { + u->in6.s6_addr[j] = 0; + continue; + } - d = delta & 0xFF; - delta >>= 8; + if (prefixlen - p < 8) { + u->in6.s6_addr[j] &= 0xff << (8 - (prefixlen - p)); + t = u->in6.s6_addr[j] + ((nth & 0xff) << (8 - (prefixlen - p))); + nth >>= prefixlen - p; + } else { + t = u->in6.s6_addr[j] + (nth & 0xff) + overflow; + nth >>= 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]; + overflow = t > UINT8_MAX; + u->in6.s6_addr[j] = (uint8_t) (t & 0xff); } - if (overflow || delta != 0) + if (overflow || nth != 0) return -ERANGE; - u->in6 = result; return 0; } diff --git a/src/test/test-in-addr-util.c b/src/test/test-in-addr-util.c index beab1caf850..c2cf26d7206 100644 --- a/src/test/test-in-addr-util.c +++ b/src/test/test-in-addr-util.c @@ -238,6 +238,8 @@ static void test_in_addr_prefix_intersect(void) { static void test_in_addr_prefix_next_one(unsigned f, const char *before, unsigned pl, const char *after) { union in_addr_union ubefore, uafter, t; + log_info("/* %s(%s, prefixlen=%u) */", __func__, before, pl); + assert_se(in_addr_from_string(f, before, &ubefore) >= 0); t = ubefore; @@ -250,13 +252,12 @@ static void test_in_addr_prefix_next_one(unsigned f, const char *before, unsigne } static void test_in_addr_prefix_next(void) { - log_info("/* %s */", __func__); - test_in_addr_prefix_next_one(AF_INET, "192.168.0.0", 24, "192.168.1.0"); test_in_addr_prefix_next_one(AF_INET, "192.168.0.0", 16, "192.169.0.0"); test_in_addr_prefix_next_one(AF_INET, "192.168.0.0", 20, "192.168.16.0"); test_in_addr_prefix_next_one(AF_INET, "0.0.0.0", 32, "0.0.0.1"); + test_in_addr_prefix_next_one(AF_INET, "255.255.255.254", 32, "255.255.255.255"); test_in_addr_prefix_next_one(AF_INET, "255.255.255.255", 32, NULL); test_in_addr_prefix_next_one(AF_INET, "255.255.255.0", 24, NULL); @@ -275,6 +276,8 @@ static void test_in_addr_prefix_next(void) { 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; + log_info("/* %s(%s, prefixlen=%u, nth=%"PRIu64") */", __func__, before, pl, nth); + assert_se(in_addr_from_string(f, before, &ubefore) >= 0); t = ubefore; @@ -287,10 +290,9 @@ static void test_in_addr_prefix_nth_one(unsigned f, const char *before, unsigned } 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, "192.168.0.123", 24, 0, "192.168.0.0"); + test_in_addr_prefix_nth_one(AF_INET, "192.168.0.123", 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"); @@ -309,6 +311,7 @@ static void test_in_addr_prefix_nth(void) { 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); + test_in_addr_prefix_nth_one(AF_INET6, "1234:5678:90ab:cdef:1234:5678:90ab:cdef", 12, 1, "1240::"); } static void test_in_addr_to_string_one(int f, const char *addr) {