是否将<netinet/in.h>协议转换为名称？

Question

中定义了一长串协议：

/*
 * Protocols (RFC 1700)
 */
#define IPPROTO_IP              0               /* dummy for IP */
#if !defined(_POSIX_C_SOURCE) || defined(_DARWIN_C_SOURCE)
#define IPPROTO_HOPOPTS 0               /* IP6 hop-by-hop options */
#endif  /* (!_POSIX_C_SOURCE || _DARWIN_C_SOURCE) */
#define IPPROTO_ICMP            1               /* control message protocol */
#if !defined(_POSIX_C_SOURCE) || defined(_DARWIN_C_SOURCE)
#define IPPROTO_IGMP            2               /* group mgmt protocol */
#define IPPROTO_GGP             3               /* gateway^2 (deprecated) */
#define IPPROTO_IPV4            4               /* IPv4 encapsulation */
#define IPPROTO_IPIP            IPPROTO_IPV4    /* for compatibility */
#endif  /* (!_POSIX_C_SOURCE || _DARWIN_C_SOURCE) */
#define IPPROTO_TCP             6               /* tcp */
#if !defined(_POSIX_C_SOURCE) || defined(_DARWIN_C_SOURCE)
#define IPPROTO_ST              7               /* Stream protocol II */

/* ... */

是否有将中定义的协议转换为名称的默认函数/调用？让chars[]作为回报的理想选择：

ipproto2str(IPPROTO_ICMP): "Control Message Protocol (ICMP)"

Answer 1

你在找getprotobynumber()。

#include <stdio.h>
#include <netdb.h>
#include <netinet/in.h>

int main(void) {
  struct protoent *p = getprotobynumber(IPPROTO_ICMP);
  if (p) {
    printf("IPPROTO_ICMP (%d) = %s\n", p->p_proto, p->p_name);
  } else {
    puts("Couldn't find IPPROTO_ICMP");
  }
}