About

isinetaddr is a simple C library that provides an interface that can be used to validate an IPv(4|6) address (with optional support for CIDR notation included). The library is guided by easy to extend testcases that help verify safety and correctness.

Examples

IPv4

The following example demonstrates the isinetaddr4 function with both valid and invalid inputs. The isinetaddr4 function returns 1 when the input given is a valid IPv4 address, and otherwise returns 0.

#include <isinetaddr.h>
#include <stdio.h>
#include <stdlib.h>

const char *valid[] = { "127.0.0.1", "1.1.1.1", "0.0.0.0" };
const char *invalid[] = { "foobar", "0.0.0.0.0", NULL };

void
validate(const char *str)
{
  if (isinetaddr4(str)) {
    printf("%s is a valid IPv4 address.\n", str);
  } else {
    printf("%s is an invalid IPv4 address.\n", str);
  }
}

int
main(void)
{
  printf("// valid\n");
  for (int i = 0; i < 3; i++) {
    validate(valid[i]);
  }
  printf("// invalid\n");
  for (int i = 0; i < 3; i++) {
    validate(invalid[i]);
  }
  return EXIT_SUCCESS;
}

Expected output:

$ cc -Iinclude src/*.c share/isinetaddr/examples/isinetaddr4.c -o example
$ ./example
// valid
127.0.0.1 is a valid IPv4 address.
1.1.1.1 is a valid IPv4 address.
0.0.0.0 is a valid IPv4 address.
// invalid
foobar is an invalid IPv4 address.
0.0.0.0.0 is an invalid IPv4 address.
(null) is an invalid IPv4 address.

CIDR notation (IPv4)

The iscidraddr4 function supports the same feature set as isinetaddr4, and in addition supports CIDR notation. The following example builds on the previous example:

#include <isinetaddr.h>
#include <stdio.h>
#include <stdlib.h>

const char *valid[] = { "127.0.0.1", "192.168.2.1/32", "192.168.2.1/0" };
const char *invalid[] = { "foobar", "0.0.0.0.0", "192.168.2.1/33" };

void
validate(const char *str)
{
  if (iscidraddr4(str)) {
    printf("%s is a valid IPv4 address.\n", str);
  } else {
    printf("%s is an invalid IPv4 address.\n", str);
  }
}

int
main(void)
{
  printf("// valid\n");
  for (int i = 0; i < 3; i++) {
    validate(valid[i]);
  }
  printf("// invalid\n");
  for (int i = 0; i < 3; i++) {
    validate(invalid[i]);
  }
  return EXIT_SUCCESS;
}

Expected output:

$ cc -Iinclude src/*.c share/isinetaddr/examples/iscidraddr4.c -o example
$ ./example
// valid
127.0.0.1 is a valid IPv4 address.
192.168.2.1/32 is a valid IPv4 address.
192.168.2.1/0 is a valid IPv4 address.
// invalid
foobar is an invalid IPv4 address.
0.0.0.0.0 is an invalid IPv4 address.
192.168.2.1/33 is an invalid IPv4 address.

IPv6

The following example demonstrates the isinetaddr6 function with both valid and invalid inputs. The isinetaddr6 function returns 1 when the input given is a valid IPv6 address, and otherwise returns 0.

#include <isinetaddr.h>
#include <stdio.h>
#include <stdlib.h>

const char *valid[] = { "::", "::1", "0000:0000:0000:0000:0000:0000:0000:0000" };
const char *invalid[] = { "foobar", "00:::0", NULL };

void
validate(const char *str)
{
  if (isinetaddr6(str)) {
    printf("%s is a valid IPv6 address.\n", str);
  } else {
    printf("%s is an invalid IPv6 address.\n", str);
  }
}

int
main(void)
{
  printf("// valid\n");
  for (int i = 0; i < 3; i++) {
    validate(valid[i]);
  }
  printf("// invalid\n");
  for (int i = 0; i < 3; i++) {
    validate(invalid[i]);
  }
  return EXIT_SUCCESS;
}

Expected output:

$ cc -Iinclude src/*.c share/isinetaddr/examples/isinetaddr6.c -o example
$ ./example
// valid
:: is a valid IPv6 address.
::1 is a valid IPv6 address.
0000:0000:0000:0000:0000:0000:0000:0000 is a valid IPv6 address.
// invalid
foobar is an invalid IPv6 address.
00:::0 is an invalid IPv6 address.
(null) is an invalid IPv6 address.

Sources

• Source code (GitHub)
• Source code (GitLab)

License

BSD Zero Clause.
See LICENSE.