getaddrinfo

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#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>

int getaddrinfo(const char *node, const char *service,
                const struct addrinfo *hints,
                struct addrinfo **res);

void freeaddrinfo(struct addrinfo *res);

char *gai_strerror(int errcode);

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getaddrinfo(3) ´Ø¿ô¤¬ºî¤ë¤³¤È¤Î¤Ç¤­¤ë¤Î¤Ï IPv4 ¥¢¥É¥ì¥¹¹½Â¤ÂΤÀ¤±¤Ç¤Ï¤Ê¤¤¡£ IPv6 ¤Î¥µ¥Ý¡¼¥È¤µ¤ì¤Æ¤¤¤ë¥·¥¹¥Æ¥à¤Ê¤é IPv6 ¤Î¥½¥±¥Ã¥È¥¢¥É¥ì¥¹¹½Â¤ÂΤâÀ¸À®¤Ç¤­¤ë¡£ ¤³¤ì¤é¤Î¥½¥±¥Ã¥È¥¢¥É¥ì¥¹¹½Â¤ÂΤϡ¢ ¥¯¥é¥¤¥¢¥ó¥È¤ä¥µ¡¼¥Ð¡¼¤Ç¥½¥±¥Ã¥È¤ò½àÈ÷¤¹¤ëºÝ¤Ë¡¢ bind(2) ¤ä connect(2) ¤«¤éľÀÜÍøÍѤǤ­¤ë¡£

¤³¤Î´Ø¿ô¤¬ÍѤ¤¤ë addrinfo ¹½Â¤ÂΤˤϰʲ¼¤Î¥á¥ó¥Ð¡¼¤¬´Þ¤Þ¤ì¤Æ¤¤¤ë¡£

struct addrinfo {
    int     ai_flags;
    int     ai_family;
    int     ai_socktype;
    int     ai_protocol;
    size_t  ai_addrlen;
    struct sockaddr *ai_addr;
    char   *ai_canonname;
    struct addrinfo *ai_next;
};

getaddrinfo(3) ¤Ï¡¢ ai_next ¥á¥ó¥Ð¡¼¤Ç¥ê¥ó¥¯¤µ¤ì¤¿ addrinfo ¹½Â¤ÂΤΥê¥ó¥¯¥ê¥¹¥È¤ò¥á¥â¥ê¾å¤ËưŪ³ä¤êÅö¤Æ¤Ë¤è¤Ã¤ÆºîÀ®¤·¡¢ res ¤Ë¤½¤ÎÀèƬ¤Ø¤Î¥Ý¥¤¥ó¥¿¤òÀßÄꤹ¤ë¡£ Ê£¿ô¤Î addrinfo ¹½Â¤ÂΤ«¤é¤Ê¤ë¥ê¥ó¥¯¥ê¥¹¥È¤òÍѤ¤¤ë¤³¤È¤Ë¤·¤¿¤Î¤Ë¤ÏÍýͳ¤¬¤¢¤ë¡£ Î㤨¤Ð¡¢¥Í¥Ã¥È¥ï¡¼¥¯¥Û¥¹¥È¤¬¥Þ¥ë¥Á¥Û¡¼¥à¤Î¾ì¹ç¤ä¡¢ Ê£¿ô¤Î¥½¥±¥Ã¥È¥×¥í¥È¥³¥ë¤ÇƱ¤¸¥µ¡¼¥Ó¥¹¤¬»È¤¨¤ë (¤Ò¤È¤Ä¤¬ SOCK_STREM ¥¢¥É¥ì¥¹¤Ç¡¢¤â¤¦¤Ò¤È¤Ä¤¬ SOCK_DGRAM ¥¢¥É¥ì¥¹¤Ç¤¢¤ë¤Ê¤É) ¾ì¹ç¤ËÅԹ礬¤¤¤¤¤«¤é¤Ç¤¢¤ë¡£

ai_family, ai_socktype, ai_protocol ¥á¥ó¥Ð¡¼¤Ï¡¢¤½¤ì¤¾¤ì socket(2) ¥·¥¹¥Æ¥à¥³¡¼¥ë¤ÎÂбþ¤¹¤ë°ú¤­¿ô¤ÈƱ¤¸°ÕÌ£¤ò»ý¤Ä¡£ getaddrinfo(3) ´Ø¿ô¤Ï IPv4 ¤¢¤ë¤¤¤Ï IPv6 ¥¢¥É¥ì¥¹¥Õ¥¡¥ß¥ê¡¼¤Î¥½¥±¥Ã¥È¥¢¥É¥ì¥¹¤òÊÖ¤¹ (ai_family ¤¬ PF_INET ¤Þ¤¿¤Ï PF_INET6 ¤Î¤¤¤º¤ì¤«¤Ë¥»¥Ã¥È¤µ¤ì¤ë)¡£

hints ¥Ñ¥é¥á¡¼¥¿¤Ë¤Ï¡¢Í¥À褵¤»¤¿¤¤¥½¥±¥Ã¥È¤Î¥¿¥¤¥× (¤¢¤ë¤¤¤Ï¥×¥í¥È¥³¥ë) ¤ò»ØÄꤹ¤ë¡£ hints ¤ò NULL ¤Ë¤¹¤ë¤³¤È¤Ï¡¢Á´¤Æ¤Î¥Í¥Ã¥È¥ï¡¼¥¯¥¢¥É¥ì¥¹/¥×¥í¥È¥³¥ë¤¬ ¼õ¤±Æþ¤ì²Äǽ¤Ç¤¢¤ë¤³¤È¤ò°ÕÌ£¤¹¤ë¡£ ¤³¤Î¥Ñ¥é¥á¡¼¥¿¤¬ NULL ¤Ç¤Ê¤¤¤È¤­¤Ï¡¢ addrinfo ¹½Â¤ÂΤò¥Ý¥¤¥ó¥È¤¹¤ë¤è¤¦¤Ë¤¹¤ë¡£ ¤³¤Î¹½Â¤ÂΤΠai_familiy, ai_socktype, ai_protocol ¥á¥ó¥Ð¡¼¤Ç¡¢Í¥À褵¤ì¤ë¥½¥±¥Ã¥È¥¿¥¤¥×¤Ê¤É¤ò»ØÄꤹ¤ë¡£ ai_family ¤Ë PF_UNSPEC ¤ò»ØÄꤹ¤ë¤È¡¢Ç¤°Õ¤Î¥×¥í¥È¥³¥ë¥Õ¥¡¥ß¥ê¡¼¤ò°ÕÌ£¤¹¤ë (Î㤨¤Ð IPv4 ¤ä IPv6)¡£ ai_socktype ¤È ai_protocol ¤Ë 0 ¤ò»ØÄꤹ¤ë¤È¡¢ ƱÍͤËǤ°Õ¤Î¥½¥±¥Ã¥È¥¿¥¤¥×¤ä¥×¥í¥È¥³¥ë¤ò¼õÉÕ¤±¤ë¤³¤È¤ò°ÕÌ£¤¹¤ë¡£ ai_flags ¥á¥ó¥Ð¡¼¤Ë¤ÏÄɲ媥ץ·¥ç¥ó¤ò»ØÄꤹ¤ë (ÄêµÁ¤Ï°Ê²¼)¡£ Ê£¿ô¤Î¥Õ¥é¥°¤ò»ØÄꤹ¤ë¤Ë¤Ï¡¢¤½¤ì¤é¤ÎÏÀÍý OR ¤ò¤È¤Ã¤Æ»ØÄꤹ¤ì¤Ð¤è¤¤¡£ hints ¥Ñ¥é¥á¡¼¥¿¤Î¤½¤Î¾¤Î¥á¥ó¥Ð¡¼¤Ë¤Ï¡¢ 0 (¤Þ¤¿¤Ï¥Ì¥ë¡¦¥Ý¥¤¥ó¥¿¡¼) ¤òÆþ¤ì¤Ê¤±¤ì¤Ð¤Ê¤é¤Ê¤¤¡£

node ¥Ñ¥é¥á¡¼¥¿¤È service ¥Ñ¥é¥á¡¼¥¿¤Î¤É¤Á¤é¤«¤Ï NULL ¤Ë¤·¤Æ¤è¤¤ (ξÊýƱ»þ¤Ë¤ÏÉÔ²Ä)¡£ node ¤Ë¤Ï¿ôÃÍ·Á¼°¤Î¥Í¥Ã¥È¥ï¡¼¥¯¥¢¥É¥ì¥¹ (IPv4 ¤Ê¤é¥É¥Ã¥È¶èÀÚ¤ê¤Î 10 ¿Ê·Á¼°¡¢ IPv6 ¤Ê¤é 16 ¿Ê·Á¼°) ¤«¡¢¤¢¤ë¤¤¤Ï¥Í¥Ã¥È¥ï¡¼¥¯¥Û¥¹¥È¤Î̾Á°¤ò»ØÄꤹ¤ë¡£ ¸å¼Ô¤Î¾ì¹ç¤Ï¡¢¤½¤Î̾Á°¤¬°ú¤±¤Æ¥Í¥Ã¥È¥ï¡¼¥¯¥¢¥É¥ì¥¹¤Î²ò·è¤¬¤Ç¤­¤ëɬÍפ¬¤¢¤ë¡£ hints ¥Ñ¥é¥á¡¼¥¿¤Î ai_flags ¥á¥ó¥Ð¡¼¤Ë AI_NUMERICHOST ¥Õ¥é¥°¤¬´Þ¤Þ¤ì¤Æ¤¤¤ë¾ì¹ç¤Ï¡¢ node ¥Ñ¥é¥á¡¼¥¿¤Ï¿ôÃÍŪ¤Ê¥Í¥Ã¥È¥ï¡¼¥¯¥¢¥É¥ì¥¹¤Ç¤Ê¤±¤ì¤Ð¤Ê¤é¤Ê¤¤¡£ AI_NUMERICHOST ¥Õ¥é¥°¤ò»È¤¨¤Ð¡¢ ¥Û¥¹¥È¤Î̾Á°°ú¤­¡¦¥¢¥É¥ì¥¹²ò·è¤ËĹ»þ´Ö¤«¤«¤Ã¤Æ¤·¤Þ¤¦²ÄǽÀ­¤òÇÓ½ü¤Ç¤­¤ë¡£

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