github.com/afumu/libc@v0.0.6/musl/src/network/getservbyport_r.c (about)

     1  #define _GNU_SOURCE
     2  #include <sys/socket.h>
     3  #include <netinet/in.h>
     4  #include <netdb.h>
     5  #include <inttypes.h>
     6  #include <errno.h>
     7  #include <string.h>
     8  #include <stdlib.h>
     9  
    10  int getservbyport_r(int port, const char *prots,
    11  	struct servent *se, char *buf, size_t buflen, struct servent **res)
    12  {
    13  	int i;
    14  	struct sockaddr_in sin = {
    15  		.sin_family = AF_INET,
    16  		.sin_port = port,
    17  	};
    18  
    19  	if (!prots) {
    20  		int r = getservbyport_r(port, "tcp", se, buf, buflen, res);
    21  		if (r) r = getservbyport_r(port, "udp", se, buf, buflen, res);
    22  		return r;
    23  	}
    24  	*res = 0;
    25  
    26  	/* Align buffer */
    27  	i = (uintptr_t)buf & sizeof(char *)-1;
    28  	if (!i) i = sizeof(char *);
    29  	if (buflen < 3*sizeof(char *)-i)
    30  		return ERANGE;
    31  	buf += sizeof(char *)-i;
    32  	buflen -= sizeof(char *)-i;
    33  
    34  	if (strcmp(prots, "tcp") && strcmp(prots, "udp")) return EINVAL;
    35  
    36  	se->s_port = port;
    37  	se->s_proto = (char *)prots;
    38  	se->s_aliases = (void *)buf;
    39  	buf += 2*sizeof(char *);
    40  	buflen -= 2*sizeof(char *);
    41  	se->s_aliases[1] = 0;
    42  	se->s_aliases[0] = se->s_name = buf;
    43  
    44  	switch (getnameinfo((void *)&sin, sizeof sin, 0, 0, buf, buflen,
    45  		strcmp(prots, "udp") ? 0 : NI_DGRAM)) {
    46  	case EAI_MEMORY:
    47  	case EAI_SYSTEM:
    48  		return ENOMEM;
    49  	default:
    50  		return ENOENT;
    51  	case 0:
    52  		break;
    53  	}
    54  
    55  	/* A numeric port string is not a service record. */
    56  	if (strtol(buf, 0, 10)==ntohs(port)) return ENOENT;
    57  
    58  	*res = se;
    59  	return 0;
    60  }