fix spurious errors from pwd/grp functions when nscd backend is absent

for several pwd/grp functions, the only way the caller can distinguish
between a successful negative result ("no such user/group") and an
internal error is by clearing errno before the call and checking errno
afterwards. the nscd backend support code correctly simulated a
not-found response on systems where such a backend is not running, but
failed to restore errno.

this commit also fixed an outdated/incorrect comment.

diff --git a/src/passwd/nscd_query.c b/src/passwd/nscd_query.c
index 69a7815..d38e371 100644 (file)
--- a/src/passwd/nscd_query.c
+++ b/src/passwd/nscd_query.c
@@ -32,6 +32,7 @@ FILE *__nscd_query(int32_t req, const char *key, int32_t *buf, size_t len, int *
                },
                .msg_iovlen = 2
        };
+       int errno_save = errno;
 
        *swap = 0;
 retry:
@@ -50,11 +51,14 @@ retry:
                return f;
 
        if (connect(fd, (struct sockaddr*)&addr, sizeof(addr)) < 0) {
-               /* If there isn't a running nscd we return -1 to indicate that
-                * that is precisely what happened
-                */
-               if (errno == EACCES || errno == ECONNREFUSED || errno == ENOENT)
+               /* If there isn't a running nscd we simulate a "not found"
+                * result and the caller is responsible for calling
+                * fclose on the (unconnected) socket. The value of
+                * errno must be left unchanged in this case.  */
+               if (errno == EACCES || errno == ECONNREFUSED || errno == ENOENT) {
+                       errno = errno_save;
                        return f;
+               }
                goto error;
        }