/* $NetBSD: inet.c,v 1.13 2020/09/07 18:37:21 christos Exp $ */ /* * The mrouted program is covered by the license in the accompanying file * named "LICENSE". Use of the mrouted program represents acceptance of * the terms and conditions listed in that file. * * The mrouted program is COPYRIGHT 1989 by The Board of Trustees of * Leland Stanford Junior University. */ #include #include "defs.h" /* buffers to hold the string representations */ /* of IP addresses, returned by inet_fmt{s}() */ #define SS_MASK ((1 << 3) - 1) static char ss[SS_MASK + 1][32]; static int ss_index = 0; /* index into above */ /* * Verify that a given IP address is credible as a host address. * (Without a mask, cannot detect addresses of the form {subnet,0} or * {subnet,-1}.) */ int inet_valid_host(u_int32_t naddr) { u_int32_t addr; addr = ntohl(naddr); return (!(IN_MULTICAST(addr) || IN_BADCLASS (addr) || (addr & 0xff000000) == 0)); } /* * Verify that a given netmask is plausible; * make sure that it is a series of 1's followed by * a series of 0's with no discontiguous 1's. */ int inet_valid_mask(u_int32_t mask) { if (~(((mask & -mask) - 1) | mask) != 0) { /* Mask is not contiguous */ return (FALSE); } return (TRUE); } /* * Verify that a given subnet number and mask pair are credible. * * With CIDR, almost any subnet and mask are credible. mrouted still * can't handle aggregated class A's, so we still check that, but * otherwise the only requirements are that the subnet address is * within the [ABC] range and that the host bits of the subnet * are all 0. */ int inet_valid_subnet(u_int32_t nsubnet, u_int32_t nmask) { u_int32_t subnet, mask; subnet = ntohl(nsubnet); mask = ntohl(nmask); if ((subnet & mask) != subnet) return (FALSE); if (subnet == 0) return (mask == 0); if (IN_CLASSA(subnet)) { if (mask < 0xff000000 || (subnet & 0xff000000) == 0x7f000000 || (subnet & 0xff000000) == 0x00000000) return (FALSE); } else if (IN_CLASSD(subnet) || IN_BADCLASS(subnet)) { /* Above Class C address space */ return (FALSE); } if (subnet & ~mask) { /* Host bits are set in the subnet */ return (FALSE); } if (!inet_valid_mask(mask)) { /* Netmask is not contiguous */ return (FALSE); } return (TRUE); } /* * Convert an IP address in u_long (network) format into a printable string. */ char * inet_fmt(u_int32_t addr) { u_char *a; char *s = ss[++ss_index & SS_MASK]; a = (u_char *)&addr; snprintf(s, sizeof ss[0], "%u.%u.%u.%u", a[0], a[1], a[2], a[3]); return (s); } /* * Convert an IP subnet number in u_long (network) format into a printable * string including the netmask as a number of bits. */ char * inet_fmts(u_int32_t addr, u_int32_t mask) { u_char *a, *m; int bits; char *s = ss[++ss_index & SS_MASK]; if ((addr == 0) && (mask == 0)) { snprintf(s, sizeof ss[0], "default"); return (s); } a = (u_char *)&addr; m = (u_char *)&mask; bits = 33 - ffs(ntohl(mask)); if (m[3] != 0) snprintf(s, sizeof ss[0], "%u.%u.%u.%u/%d", a[0], a[1], a[2], a[3], bits); else if (m[2] != 0) snprintf(s, sizeof ss[0], "%u.%u.%u/%d", a[0], a[1], a[2], bits); else if (m[1] != 0) snprintf(s, sizeof ss[0], "%u.%u/%d", a[0], a[1], bits); else snprintf(s, sizeof ss[0], "%u/%d", a[0], bits); return (s); } /* * Convert the printable string representation of an IP address into the * u_long (network) format. Return 0xffffffff on error. (To detect the * legal address with that value, you must explicitly compare the string * with "255.255.255.255".) */ u_int32_t inet_parse(char *s, int *mask_p) { u_int32_t a = 0; u_int a0, a1, a2, a3; char c; int n; if (sscanf(s, "%u.%u.%u.%u%n", &a0, &a1, &a2, &a3, &n) != 4) return 0xffffffff; if (a0 > 255 || a1 > 255 || a2 > 255 || a3 > 255) return 0xffffffff; if (mask_p == 0) { if (s[n] != 0) return 0xffffffff; } else { if (sscanf(s + n, "/%u%c", &n, &c) != 1 || n > 32) return 0xffffffff; *mask_p = n; } ((u_char *)&a)[0] = a0; ((u_char *)&a)[1] = a1; ((u_char *)&a)[2] = a2; ((u_char *)&a)[3] = a3; return (a); } /* * inet_cksum extracted from: * P I N G . C * * Author - * Mike Muuss * U. S. Army Ballistic Research Laboratory * December, 1983 * Modified at Uc Berkeley * * (ping.c) Status - * Public Domain. Distribution Unlimited. * * I N _ C K S U M * * Checksum routine for Internet Protocol family headers (C Version) * */ int inet_cksum(const void *addr, u_int len) { int nleft = (int)len; const u_int16_t *w = addr; int32_t sum = 0; union { u_int16_t w; u_int8_t b[2]; } answer; assert(((uintptr_t)w & 1) == 0); /* * Our algorithm is simple, using a 32 bit accumulator (sum), * we add sequential 16 bit words to it, and at the end, fold * back all the carry bits from the top 16 bits into the lower * 16 bits. */ while (nleft > 1) { sum += *w++; nleft -= 2; } /* mop up an odd byte, if necessary */ if (nleft == 1) { answer.w = 0; answer.b[0] = *(const u_char *)w; sum += answer.w; } /* * add back carry outs from top 16 bits to low 16 bits */ sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */ sum += (sum >> 16); /* add carry */ answer.w = ~sum; /* truncate to 16 bits */ return (answer.w); }