X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=blobdiff_plain;f=src%2Fshared%2Fin-addr-util.c;h=d88864b5987f7387ebd99e2ea9a689d05038c478;hb=30ab6a0fc1bb950c4dcd90dcd3dfe00a810c7fc1;hp=459f8461738f935fc0c09af5ce6e70e00af3c5d6;hpb=af93291cc4cbd2fe2fb4af7d3c56138fb39f31dc;p=elogind.git

diff --git a/src/shared/in-addr-util.c b/src/shared/in-addr-util.c
index 459f84617..d88864b59 100644
--- a/src/shared/in-addr-util.c
+++ b/src/shared/in-addr-util.c
@@ -242,3 +242,97 @@ int in_addr_from_string_auto(const char *s, int *family, union in_addr_union *re
 
         return -EINVAL;
 }
+
+unsigned char in_addr_netmask_to_prefixlen(const struct in_addr *addr) {
+        assert(addr);
+
+        return 32 - u32ctz(be32toh(addr->s_addr));
+}
+
+struct in_addr* in_addr_prefixlen_to_netmask(struct in_addr *addr, unsigned char prefixlen) {
+        assert(addr);
+        assert(prefixlen <= 32);
+
+        /* Shifting beyond 32 is not defined, handle this specially. */
+        if (prefixlen == 0)
+                addr->s_addr = 0;
+        else
+                addr->s_addr = htobe32((0xffffffff << (32 - prefixlen)) & 0xffffffff);
+
+        return 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;
+
+        in_addr_prefixlen_to_netmask(mask, prefixlen);
+        return 0;
+}
+
+int in_addr_mask(int family, union in_addr_union *addr, unsigned char prefixlen) {
+        assert(addr);
+
+        if (family == AF_INET) {
+                struct in_addr mask;
+
+                if (!in_addr_prefixlen_to_netmask(&mask, prefixlen))
+                        return -EINVAL;
+
+                addr->in.s_addr &= mask.s_addr;
+                return 0;
+        }
+
+        if (family == AF_INET6) {
+                unsigned i;
+
+                for (i = 0; i < 16; i++) {
+                        uint8_t mask;
+
+                        if (prefixlen >= 8) {
+                                mask = 0xFF;
+                                prefixlen -= 8;
+                        } else {
+                                mask = 0xFF << (8 - prefixlen);
+                                prefixlen = 0;
+                        }
+
+                        addr->in6.s6_addr[i] &= mask;
+                }
+
+                return 0;
+        }
+
+        return -EAFNOSUPPORT;
+}