Using AI_CANONNAME on systems that do not defined AI_FQDN causes BADFLAGS error

[naost3rn]

Executing the following test code in Alpine Linux will result in a BADFLAGS error.

#include <sys/types.h>
#include <sys/socket.h>
#include <errno.h>
#include <netdb.h>
#include <stdio.h>
#include <string.h>
#include <asr.h>

int main() {
    struct asr_query *query;
    struct asr_result result;
    struct addrinfo hints;
    const char *hostname = "www.yahoo.co.jp";

    memset(&hints, 0, sizeof(hints));
    hints.ai_flags = AI_CANONNAME;
    query = getaddrinfo_async(hostname, NULL, &hints, NULL);
    asr_run_sync(query, &result);
    if (errno != 0) {
        printf("asr run error: %s\n", strerror(errno));
        return 1;
    } else if (result.ar_gai_errno) {
        printf("gataddrinfo error: %s\n", gai_strerror(result.ar_gai_errno));
        return 1;
    }
    return 0;
}

$ cc test.c ./libopenbsd.a
$ ./a.out 
gataddrinfo error: Invalid flags

Only of the AI_CANONNAME and AI_FQDN bits can be set, Only the AI_CANONNAME and AI_FQDN bits can be set, and are verified in getaddrinfo_async_run() as follows:

OpenSMTPD/openbsd-compat/libasr/getaddrinfo_async.c

Lines 166 to 171 in bf2a083

	if (ai->ai_flags & ~AI_MASK ||
	(ai->ai_flags & AI_CANONNAME && ai->ai_flags & AI_FQDN)) {
	ar->ar_gai_errno = EAI_BADFLAGS;
	async_set_state(as, ASR_STATE_HALT);
	break;
	}

But, on systems such as Linux with musl that do not define AI_FQDN, it is defined as AI_CANONNAME at build time:

OpenSMTPD/openbsd-compat/libasr/asr_compat.h

Lines 49 to 51 in bf2a083

	#ifndef AI_FQDN
	#define AI_FQDN AI_CANONNAME
	#endif

However, smtpd is not affected by this issue because the AI_CANONNAME flag is used by libc's getaddrinfo().

OpenSMTPD/usr.sbin/smtpd/util.c

Lines 769 to 770 in bf2a083

	hints.ai_flags = AI_CANONNAME;
	error = getaddrinfo(hostname, NULL, &hints, &res);

[omar-polo]

Thanks for moving the issue here. I'll take a look in the following days.