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authorRich Felker <dalias@aerifal.cx>2015-10-26 18:42:22 -0400
committerRich Felker <dalias@aerifal.cx>2015-10-26 18:42:22 -0400
commit2683e267fa6c20d2e7a498a85f79a1dfc4301f23 (patch)
tree27b7c8e3e3888b65dd788e6919a30a5b2deca3d5 /src/network/lookup_name.c
parentb114190b29417fff6f701eea3a3b3b6030338280 (diff)
downloadmusl-2683e267fa6c20d2e7a498a85f79a1dfc4301f23.tar.gz
safely handle failure to open hosts, services, resolv.conf files
previously, transient failures like fd exhaustion or other resource-related errors were treated the same as non-existence of these files, leading to fallbacks or false-negative results. in particular: - failure to open hosts resulted in fallback to dns, possibly yielding EAI_NONAME for a hostname that should be defined locally, or an unwanted result from dns that the hosts file was intended to replace. - failure to open services resulted in EAI_SERVICE. - failure to open resolv.conf resulted in querying localhost rather than the configured nameservers. now, only permanent errors trigger the fallback behaviors above; all other errors are reportable to the caller as EAI_SYSTEM.
Diffstat (limited to 'src/network/lookup_name.c')
-rw-r--r--src/network/lookup_name.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/src/network/lookup_name.c b/src/network/lookup_name.c
index 0225a934..df9e623e 100644
--- a/src/network/lookup_name.c
+++ b/src/network/lookup_name.c
@@ -9,6 +9,7 @@
#include <fcntl.h>
#include <unistd.h>
#include <pthread.h>
+#include <errno.h>
#include "lookup.h"
#include "stdio_impl.h"
#include "syscall.h"
@@ -51,7 +52,14 @@ static int name_from_hosts(struct address buf[static MAXADDRS], char canon[stati
int cnt = 0;
unsigned char _buf[1032];
FILE _f, *f = __fopen_rb_ca("/etc/hosts", &_f, _buf, sizeof _buf);
- if (!f) return 0;
+ if (!f) switch (errno) {
+ case ENOENT:
+ case ENOTDIR:
+ case EACCES:
+ return 0;
+ default:
+ return EAI_SYSTEM;
+ }
while (fgets(line, sizeof line, f) && cnt < MAXADDRS) {
char *p, *z;