When trying to resolve a hostname by getaddrinfo() using some specific settings, it will always return -EAI_NONAME (Name or service not known). To reproduce this behavior, you need to request an IPv6 address with the additional AF_V4MAPPED flag set from an non IPv6 capable hostname. If you choose a IPv4/IPv6 capable hostname like google.com, everything works fine. This patch is more or less a port [1][2] from the glibc and their behavior for the AF_V4MAPPED flag. To test the bug you can use the following snippet. ---- 8< ---- int ret; struct addrinfo* result; struct addrinfo hints; memset(&hints, 0, sizeof(struct addrinfo)); hints.ai_family = AF_INET6; hints.ai_flags = AI_V4MAPPED; ret = getaddrinfo("test.com", NULL, &hints, &result); printf("getaddrinfo(): %i", ret); ---- 8< ---- [1] https://sourceware.org/git/?p=glibc.git;a=commit;f=sysdeps/posix/getaddrinf… [2] https://sourceware.org/git/?p=glibc.git;a=commit;f=sysdeps/posix/getaddrinf… Signed-off-by: Alexander Wenzel &lt;alexander.wenzel(a)qsc.de&gt; --- libc/inet/getaddrinfo.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/libc/inet/getaddrinfo.c b/libc/inet/getaddrinfo.c index 7ae32be..a9000ae 100644 --- a/libc/inet/getaddrinfo.c +++ b/libc/inet/getaddrinfo.c @@ -391,6 +391,9 @@ static uint8_t __gai_precedence = 0; /* =1 - IPv6, IPv4 memcpy((*pat)->addr, h->h_addr_list[i], sizeof(_type)); \ pat = &((*pat)->next); \ } \ + if (_family == AF_INET6 && i > 0) { \ + got_ipv6 = true; \ + } \ } \ } @@ -404,6 +407,7 @@ gaih_inet(const char *name, const struct gaih_service *service, struct gaih_servtuple *st; struct gaih_addrtuple *at; int rc; + bool got_ipv6 = false; int v4mapped = req->ai_family == PF_INET6 && (req->ai_flags & AI_V4MAPPED); unsigned seen = 0; if (req->ai_flags & AI_ADDRCONFIG) { @@ -586,7 +590,7 @@ gaih_inet(const char *name, const struct gaih_service *service, #endif if (req->ai_family == AF_INET || (!v4mapped && req->ai_family == AF_UNSPEC) - || (v4mapped && (no_inet6_data != 0 || (req->ai_flags & AI_ALL))) + || (v4mapped && (!got_ipv6 || (req->ai_flags & AI_ALL))) ) { if (!(req->ai_flags & AI_ADDRCONFIG) || (seen & SEEN_IPV4)) gethosts(AF_INET, struct in_addr); @@ -705,6 +709,14 @@ gaih_inet(const char *name, const struct gaih_service *service, if (at2->family == AF_INET6 || v4mapped) { family = AF_INET6; socklen = sizeof(struct sockaddr_in6); + + /* If we looked up IPv4 mapped address discard them here if + the caller isn't interested in all address and we have + found at least one IPv6 address. */ + if (got_ipv6 + && (req->ai_flags & (AI_V4MAPPED|AI_ALL)) == AI_V4MAPPED + && IN6_IS_ADDR_V4MAPPED (at2->addr)) + goto ignore; } #endif #if defined __UCLIBC_HAS_IPV4__ && defined __UCLIBC_HAS_IPV6__ @@ -781,7 +793,7 @@ gaih_inet(const char *name, const struct gaih_service *service, (*pai)->ai_next = NULL; pai = &((*pai)->ai_next); } - +ignore: at2 = at2->next; } } -- 2.1.4