diff options
Diffstat (limited to 'resolv/resolv_conf.c')
| -rw-r--r-- | resolv/resolv_conf.c | 86 |
1 files changed, 85 insertions, 1 deletions
diff --git a/resolv/resolv_conf.c b/resolv/resolv_conf.c index dd66523992..9ef59240eb 100644 --- a/resolv/resolv_conf.c +++ b/resolv/resolv_conf.c @@ -22,6 +22,7 @@ #include <assert.h> #include <libc-lock.h> #include <resolv-internal.h> +#include <sys/stat.h> /* _res._u._ext.__glibc_extension_index is used as an index into a struct resolv_conf_array object. The intent of this construction @@ -54,6 +55,15 @@ struct resolv_conf_global the array element is overwritten with NULL. */ struct resolv_conf_array array; + /* Cached current configuration object for /etc/resolv.conf. */ + struct resolv_conf *conf_current; + + /* These properties of /etc/resolv.conf are used to check if the + configuration needs reloading. */ + struct timespec conf_mtime; + struct timespec conf_ctime; + off64_t conf_size; + ino64_t conf_ino; }; /* Lazily allocated storage for struct resolv_conf_global. */ @@ -100,6 +110,75 @@ conf_decrement (struct resolv_conf *conf) free (conf); } +struct resolv_conf * +__resolv_conf_get_current (void) +{ + struct stat64 st; + if (stat64 (_PATH_RESCONF, &st) != 0) + { + switch (errno) + { + case EACCES: + case EISDIR: + case ELOOP: + case ENOENT: + case ENOTDIR: + case EPERM: + /* Ignore errors due to file system contents. */ + memset (&st, 0, sizeof (st)); + break; + default: + /* Other errors are fatal. */ + return NULL; + } + } + + struct resolv_conf_global *global_copy = get_locked_global (); + if (global_copy == NULL) + return NULL; + struct resolv_conf *conf; + if (global_copy->conf_current != NULL + && (global_copy->conf_mtime.tv_sec == st.st_mtim.tv_sec + && global_copy->conf_mtime.tv_nsec == st.st_mtim.tv_nsec + && global_copy->conf_ctime.tv_sec == st.st_ctim.tv_sec + && global_copy->conf_ctime.tv_nsec == st.st_ctim.tv_nsec + && global_copy->conf_ino == st.st_ino + && global_copy->conf_size == st.st_size)) + /* We can reuse the cached configuration object. */ + conf = global_copy->conf_current; + else + { + /* Parse configuration while holding the lock. This avoids + duplicate work. */ + conf = __resolv_conf_load (NULL); + if (conf != NULL) + { + if (global_copy->conf_current != NULL) + conf_decrement (global_copy->conf_current); + global_copy->conf_current = conf; /* Takes ownership. */ + + /* Update file modification stamps. The configuration we + read could be a newer version of the file, but this does + not matter because this will lead to an extraneous reload + later. */ + global_copy->conf_mtime = st.st_mtim; + global_copy->conf_ctime = st.st_ctim; + global_copy->conf_ino = st.st_ino; + global_copy->conf_size = st.st_size; + } + } + + if (conf != NULL) + { + /* Return an additional reference. */ + assert (conf->__refcount > 0); + ++conf->__refcount; + assert (conf->__refcount > 0); + } + put_locked_global (global_copy); + return conf; +} + /* Internal implementation of __resolv_conf_get, without validation against *RESP. */ static struct resolv_conf * @@ -320,7 +399,6 @@ __resolv_conf_allocate (const struct resolv_conf *init) conf->retry = init->retry; conf->options = init->options; conf->ndots = init->ndots; - conf->initstamp = __res_initstamp; /* Allocate the arrays with pointers. These must come first because they have the highets alignment. */ @@ -580,6 +658,12 @@ freeres (void) if (global == NULL) return; + if (global->conf_current != NULL) + { + conf_decrement (global->conf_current); + global->conf_current = NULL; + } + /* Note that this frees only the array itself. The pointed-to configuration objects should have been deallocated by res_nclose and per-thread cleanup functions. */ |