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utils-cidr

utilities to manipulate CIDR ip-ranges git clone https://anongit.hacktivis.me/git/utils-cidr.git

cidr2list.c (3579B)

    

  1. // Copyright © 2025 Haelwenn (lanodan) Monnier <contact+utils-cidr@hacktivis.me>
  2. // SPDX-License-Identifier: MPL-2.0
  4. #define _POSIX_C_SOURCE 202405L
  5. #include <ctype.h>
  6. #include <endian.h>
  7. #include <errno.h>
  8. #include <inttypes.h>
  9. #include <stdbool.h>
  10. #include <stdio.h>
  11. #include <stdlib.h>
  12. #include <string.h>
  14. struct inet4_cidr
  15. {
  16. 	uint32_t addr;
  17. 	uint8_t cidr;
  18. 	uint32_t nmask;
  19. };
  21. bool
  22. str_inet4(const char *str, size_t size, struct inet4_cidr *res)
  23. {
  24. 	uint8_t dot[4] = {0, 0, 0, 0};
  25. 	uint8_t cidr = 32;
  27. 	uint8_t di = 0;
  28. 	for(size_t i = 0; i < size; i++)
  29. 	{
  30. 		if(str[i] == '.')
  31. 		{
  32. 			di++;
  33. 			if(di == 4)
  34. 			{
  35. 				fprintf(
  36. 				    stderr, "cird2list: error: Invalid IPv4 address, found more than 4 dots: %s\n", str);
  37. 				return false;
  38. 			}
  39. 			continue;
  40. 		}
  42. 		if(isdigit(str[i]))
  43. 		{
  44. 			dot[di] *= 10;
  45. 			dot[di] += str[i] - '0';
  46. 			continue;
  47. 		}
  49. 		if(i > 1 && str[i] == '/' && i + 1 < size && isdigit(str[i + 1]))
  50. 		{
  51. 			i++;
  52. 			cidr = str[i] - '0';
  54. 			if(i + 1 < size && isdigit(str[i + 1]))
  55. 			{
  56. 				i++;
  57. 				cidr *= 10;
  58. 				cidr += str[i] - '0';
  59. 			}
  61. 			if(cidr > 32)
  62. 			{
  63. 				fprintf(stderr, "cird2list: error: CIDR suffix (/%d) is higher than /32: %s\n", cidr, str);
  64. 				return false;
  65. 			}
  67. 			break;
  68. 		}
  70. 		fprintf(stderr, "cird2list: error: Invalid IPv4 address, found '%c' (0x%X)\n", str[i], str[i]);
  71. 		return false;
  72. 	}
  74. 	if(di != 3)
  75. 	{
  76. 		fprintf(
  77. 		    stderr, "cird2list: error: Invalid IPv4 address, found %d dots, expected 3: %s\n", di, str);
  78. 		return false;
  79. 	}
  81. #if 0
  82. 	fprintf(stderr, "cird2list: DEBUG: %s -> %d.%d.%d.%d/%d\n", str, dot[0], dot[1], dot[2], dot[3], cidr);
  83. #endif
  85. 	uint32_t nmask = 0xFFFFFFFFUL;
  86. 	switch(cidr)
  87. 	{
  88. 	// Make sure to avoid overflow
  89. 	case 0:
  90. 		nmask = 0;
  91. 		break;
  92. 	// 2^(32-cidr) - 1
  93. 	default:
  94. 		nmask ^= (1 << (32 - cidr)) - 1;
  95. 	}
  96. #if 0
  97. 	fprintf(stderr, "cird2list: DEBUG: nmask (/%d): ", cidr);
  98. 	fprintf(stderr, "%d.%d.%d.%d\n", (nmask >> 24) & 0xFF, (nmask >> 16) & 0xFF, (nmask >> 8) & 0xFF, (nmask) & 0xFF);
  99. #endif
  101. 	res->addr = (dot[0] << 24) | (dot[1] << 16) | (dot[2] << 8) | dot[3];
  102. 	res->cidr = cidr;
  103. 	res->nmask = nmask;
  105. 	return true;
  106. }
  108. int
  109. main(void)
  110. {
  111. 	char *buf = NULL;
  112. 	size_t buflen = 0;
  114. 	while(true)
  115. 	{
  116. 		errno = 0;
  117. 		ssize_t nread = getline(&buf, &buflen, stdin);
  118. 		if(nread < 0)
  119. 		{
  120. 			if(errno == 0) break;
  122. 			fprintf(stderr, "cird2list: error: Failed reading line: %s\n", strerror(errno));
  123. 			return 1;
  124. 		}
  126. 		char *line = buf;
  127. 		size_t linelen = nread;
  129. 		// ltrim
  130. 		while(line - buf < nread && isspace(*line))
  131. 			line++, linelen--;
  132. 		// rtrim
  133. 		for(int i = linelen - 1; (i > 0) && isspace(line[i]); i--)
  134. 			line[--linelen] = '\0';
  136. 		if(linelen <= 0) continue;
  138. 		struct inet4_cidr addr;
  139. 		if(!str_inet4(line, linelen, &addr)) return 1;
  141. 		uint32_t start = addr.addr & addr.nmask;
  142. #if 0
  143. 		fprintf(stderr, "cird2list: DEBUG: start: ");
  144. 		fprintf(stderr, "%d.%d.%d.%d\n", (start >> 24) & 0xFF, (start >> 16) & 0xFF, (start >> 8) & 0xFF, start & 0xFF);
  145. #endif
  147. 		uint32_t end = start | (addr.nmask ^ 0xFFFFFFFFUL);
  148. #if 0
  149. 		fprintf(stderr, "cird2list: DEBUG: end: ");
  150. 		fprintf(stderr, "%d.%d.%d.%d\n", (end >> 24) & 0xFF, (end >> 16) & 0xFF, (end >> 8) & 0xFF, end & 0xFF);
  151. #endif
  153. 		bool frontier = false;
  154. 		if(end == 0xFFFFFFFFUL)
  155. 		{
  156. 			// Otherwise for-loop overflows and goes loopy due to
  157. 			// the `<=` comparison which works for all other cases
  158. 			end--;
  159. 			frontier = true;
  160. 		}
  162. 		for(uint32_t ai = start; ai <= end; ai++)
  163. 		{
  164. 			printf("%d.%d.%d.%d\n", (ai >> 24) & 0xFF, (ai >> 16) & 0xFF, (ai >> 8) & 0xFF, ai & 0xFF);
  165. 		}
  167. 		if(frontier) puts("255.255.255.255");
  168. 	}
  170. 	free(buf);
  171. 	return 0;
  172. }