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in-addr-util: introduce in_addr_prefix_nth

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This commit is contained in:
Andreas Rammhold 2020-05-14 00:52:18 +02:00
parent 76410e9849
commit 863b99cdd9
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3 changed files with 127 additions and 0 deletions
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86
src/basic/in-addr-util.c
View File

@ -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,

1
src/basic/in-addr-util.h
View File

@ -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);

40
src/test/test-socket-util.c
View File

@ -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();