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authorRich Felker <dalias@aerifal.cx>2013-11-30 13:33:29 -0500
committerRich Felker <dalias@aerifal.cx>2013-11-30 13:33:29 -0500
commit7603c5f127316e5ee4c5b161d87742d2ac824567 (patch)
tree517f51c517959d8987fd08e0bc8a1226d5d0fdca
parent8c8cf4bbd269d0535cad48f4088083b5a466803f (diff)
downloadmusl-7603c5f127316e5ee4c5b161d87742d2ac824567.tar.gz
support mix of IPv4 and v6 nameservers in resolv.conf
a v6 socket will only be used if there is at least one v6 nameserver address. if the kernel lacks v6 support, the code will fall back to using a v4 socket and requests to v6 servers will silently fail. when using a v6 socket, v4 addresses are converted to v4-mapped form and setsockopt is used to ensure that the v6 socket can accept both v4 and v6 traffic (this is on-by-default on Linux but the default is configurable in /proc and so it needs to be set explicitly on the socket level). this scheme avoids increasing resource usage during lookups and allows the existing network io loop to be used without modification. previously, nameservers whose address family did not match the address family of the first-listed nameserver were simply ignored. prior to recent __ipparse fixes, they were not ignored but erroneously parsed.
-rw-r--r--src/network/__dns.c36
1 files changed, 31 insertions, 5 deletions
diff --git a/src/network/__dns.c b/src/network/__dns.c
index 8f3c6370..97d8031c 100644
--- a/src/network/__dns.c
+++ b/src/network/__dns.c
@@ -11,6 +11,7 @@
#include <ctype.h>
#include <unistd.h>
#include <pthread.h>
+#include <errno.h>
#include "__dns.h"
#include "stdio_impl.h"
@@ -35,9 +36,9 @@ int __dns_doqueries(unsigned char *dest, const char *name, int *rr, int rrcnt)
struct sockaddr_in sin;
struct sockaddr_in6 sin6;
} sa = {0}, ns[3] = {{0}};
- socklen_t sl;
+ socklen_t sl = sizeof sa.sin;
int nns = 0;
- int family = AF_UNSPEC;
+ int family = AF_INET;
unsigned char q[280] = "", *r = dest;
int ql;
int rlen;
@@ -75,10 +76,12 @@ int __dns_doqueries(unsigned char *dest, const char *name, int *rr, int rrcnt)
for (s=line+11; isspace(*s); s++);
for (z=s; *z && !isspace(*z); z++);
*z=0;
- if (__ipparse(ns+nns, family, s) < 0) continue;
+ if (__ipparse(ns+nns, AF_UNSPEC, s) < 0) continue;
ns[nns].sin.sin_port = htons(53);
- family = ns[nns++].sin.sin_family;
- sl = family==AF_INET6 ? sizeof sa.sin6 : sizeof sa.sin;
+ if (ns[nns++].sin.sin_family == AF_INET6) {
+ family = AF_INET6;
+ sl = sizeof sa.sin6;
+ }
}
if (f) __fclose_ca(f);
if (!nns) {
@@ -93,6 +96,29 @@ int __dns_doqueries(unsigned char *dest, const char *name, int *rr, int rrcnt)
sa.sin.sin_family = family;
fd = socket(family, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+ /* Handle case where system lacks IPv6 support */
+ if (fd < 0 && errno == EAFNOSUPPORT) {
+ if (family != AF_INET6) return EAI_SYSTEM;
+ fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+ family = AF_INET;
+ }
+ if (fd < 0) return EAI_SYSTEM;
+
+ /* Convert any IPv4 addresses in a mixed environment to v4-mapped */
+ if (family == AF_INET6) {
+ setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &(int){0}, sizeof 0);
+ for (i=0; i<nns; i++) {
+ if (ns[i].sin.sin_family != AF_INET) continue;
+ memcpy(ns[i].sin6.sin6_addr.s6_addr+12,
+ &ns[i].sin.sin_addr, 4);
+ memcpy(ns[i].sin6.sin6_addr.s6_addr,
+ "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
+ ns[i].sin6.sin6_family = AF_INET6;
+ ns[i].sin6.sin6_flowinfo = 0;
+ ns[i].sin6.sin6_scope_id = 0;
+ }
+ }
+
pthread_cleanup_push(cleanup, (void *)(intptr_t)fd);
pthread_setcancelstate(cs, 0);