diff options
Diffstat (limited to 'shared/systemd/src/basic/in-addr-util.c')
| -rw-r--r-- | shared/systemd/src/basic/in-addr-util.c | 74 |
1 files changed, 58 insertions, 16 deletions
diff --git a/shared/systemd/src/basic/in-addr-util.c b/shared/systemd/src/basic/in-addr-util.c index 0e770621..cddc269f 100644 --- a/shared/systemd/src/basic/in-addr-util.c +++ b/shared/systemd/src/basic/in-addr-util.c @@ -180,47 +180,89 @@ 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. */ + * positive if that succeeds, or -ERANGE if this overflows. */ + + return in_addr_prefix_nth(family, u, prefixlen, 1); +} + +/* + * 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 0; + return -ERANGE; - if (family == AF_INET) { - uint32_t c, n; + 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); - n = c + (1UL << (32 - prefixlen)); - if (n < c) - return 0; - n &= 0xFFFFFFFFUL << (32 - prefixlen); + 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 add = {}, result; + struct in6_addr result = {}; uint8_t overflow = 0; - unsigned i; + 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 */ - add.s6_addr[(prefixlen-1) / 8] = 1 << (7 - (prefixlen-1) % 8); + delta = nth << ((128 - prefixlen) % 8); - for (i = 16; i > 0; i--) { + for (unsigned i = 16; i > 0; i--) { unsigned j = i - 1; + unsigned d = 0; - 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 (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) - return 0; + if (overflow || delta != 0) + return -ERANGE; u->in6 = result; return 1; |