getaddrinfo/AI_ADDRCONFIG with ipv6 disabled

[Bob Richmond <robert.richmond@greenwavesystems.com>]

[-- Attachment #1: Type: text/plain, Size: 1054 bytes --]

connect() to the IPv6 loopback address can fail with EACCES on Linux if 
IPv6 is disabled on the lo interface, and causes getaddrinfo to fail 
without returning IPv4 addresses. It should be treated as if IPv6 is 
disabled.

echo 1 >/proc/sys/net/ipv6/conf/lo/disable_ipv6

struct addrinfo hints, *res = NULL;
hints.ai_family = PF_UNSPEC;
hints.ai_flags = AI_ADDRCONFIG;
getaddrinfo("192.168.1.1", "80", &hints, &res);

strace:
======start=======
socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC, IPPROTO_UDP) = 14
connect(14, {sa_family=AF_INET, sin_port=htons(65535), 
sin_addr=inet_addr("127.0.0.1")}, 16) = 0
close(14)                         = 0 

socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC, IPPROTO_UDP) = 14 

connect(14, {sa_family=AF_INET6, sin6_port=htons(65535), 
inet_pton(AF_INET6, "::1", &sin6_addr), sin6_flowinfo=htonl(0), 
sin6_scope_id=0}, 28) = -1 EACCES (Permission denied)
close(14)                         = 0
writev(2, [{iov_base="[warn] getaddrinfo: Permission denied\n", 
iov_len=38}, {iov_base=NULL, iov_len=0}], 2) = 38
======end=========

[-- Attachment #2: musl-getaddrinfo-ipv6-eacces.patch --]
[-- Type: text/x-patch, Size: 304 bytes --]

--- musl-1.1.24/src/network/getaddrinfo.c	2019-10-13 14:58:27.000000000 -0700
+++ musl-1.1.24/src/network/getaddrinfo.c	2019-12-04 14:52:11.003784091 -0800
@@ -76,6 +76,7 @@
 			case EHOSTUNREACH:
 			case ENETDOWN:
 			case ENETUNREACH:
+			case EACCES:
 				break;
 			default:
 				return EAI_SYSTEM;