Cleanup alias module handler register/unregister.
- Remove locking, since all module(9) events are running under &Giant. - Use TAILQ for protocol handlers and fix a bug which led to infinite cycle. Bug found in VirtualBox [1] - Simplify code everywhere. - Fix documentation. [1] https://www.virtualbox.org/pipermail/vbox-dev/2013-November/011936.html PR: 183792 [1] Submitted by: Valery Ushakov <uwe NetBSD.org> [1] Sponsored by: Nginx, Inc.
This commit is contained in:
Gleb Smirnoff
parent
2fb87f0892
commit
535e0a0981
@ -349,24 +349,16 @@ MODULE_VERSION(libalias, 1);
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static int
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alias_mod_handler(module_t mod, int type, void *data)
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{
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int error;
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switch (type) {
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case MOD_LOAD:
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error = 0;
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handler_chain_init();
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break;
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case MOD_QUIESCE:
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case MOD_UNLOAD:
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handler_chain_destroy();
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finishoff();
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error = 0;
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break;
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case MOD_LOAD:
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return (0);
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default:
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error = EINVAL;
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return (EINVAL);
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}
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return (error);
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}
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static moduledata_t alias_mod = {
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@ -52,201 +52,82 @@ __FBSDID("$FreeBSD$");
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#endif
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/* Protocol and userland module handlers chains. */
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LIST_HEAD(handler_chain, proto_handler) handler_chain = LIST_HEAD_INITIALIZER(handler_chain);
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#ifdef _KERNEL
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struct rwlock handler_rw;
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#endif
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SLIST_HEAD(dll_chain, dll) dll_chain = SLIST_HEAD_INITIALIZER(dll_chain);
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#ifdef _KERNEL
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#define LIBALIAS_RWLOCK_INIT() \
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rw_init(&handler_rw, "Libalias_modules_rwlock")
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#define LIBALIAS_RWLOCK_DESTROY() rw_destroy(&handler_rw)
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#define LIBALIAS_WLOCK_ASSERT() \
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rw_assert(&handler_rw, RA_WLOCKED)
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static __inline void
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LIBALIAS_RLOCK(void)
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{
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rw_rlock(&handler_rw);
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}
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static __inline void
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LIBALIAS_RUNLOCK(void)
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{
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rw_runlock(&handler_rw);
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}
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static __inline void
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LIBALIAS_WLOCK(void)
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{
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rw_wlock(&handler_rw);
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}
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static __inline void
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LIBALIAS_WUNLOCK(void)
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{
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rw_wunlock(&handler_rw);
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}
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static void
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_handler_chain_init(void)
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{
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if (!rw_initialized(&handler_rw))
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LIBALIAS_RWLOCK_INIT();
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}
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static void
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_handler_chain_destroy(void)
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{
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if (rw_initialized(&handler_rw))
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LIBALIAS_RWLOCK_DESTROY();
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}
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#else
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#define LIBALIAS_RWLOCK_INIT() ;
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#define LIBALIAS_RWLOCK_DESTROY() ;
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#define LIBALIAS_WLOCK_ASSERT() ;
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#define LIBALIAS_RLOCK() ;
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#define LIBALIAS_RUNLOCK() ;
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#define LIBALIAS_WLOCK() ;
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#define LIBALIAS_WUNLOCK() ;
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#define _handler_chain_init() ;
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#define _handler_chain_destroy() ;
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#endif
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void
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handler_chain_init(void)
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{
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_handler_chain_init();
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}
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void
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handler_chain_destroy(void)
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{
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_handler_chain_destroy();
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}
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static TAILQ_HEAD(handler_chain, proto_handler) handler_chain =
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TAILQ_HEAD_INITIALIZER(handler_chain);
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static int
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_attach_handler(struct proto_handler *p)
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attach_handler(struct proto_handler *p)
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{
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struct proto_handler *b;
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LIBALIAS_WLOCK_ASSERT();
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b = NULL;
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LIST_FOREACH(b, &handler_chain, entries) {
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TAILQ_FOREACH(b, &handler_chain, link) {
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if ((b->pri == p->pri) &&
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(b->dir == p->dir) &&
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(b->proto == p->proto))
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return (EEXIST); /* Priority conflict. */
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return (EEXIST);
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if (b->pri > p->pri) {
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LIST_INSERT_BEFORE(b, p, entries);
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TAILQ_INSERT_BEFORE(b, p, link);
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return (0);
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}
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}
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/* End of list or found right position, inserts here. */
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if (b)
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LIST_INSERT_AFTER(b, p, entries);
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else
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LIST_INSERT_HEAD(&handler_chain, p, entries);
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TAILQ_INSERT_TAIL(&handler_chain, p, link);
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return (0);
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}
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static int
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_detach_handler(struct proto_handler *p)
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{
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struct proto_handler *b, *b_tmp;
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LIBALIAS_WLOCK_ASSERT();
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LIST_FOREACH_SAFE(b, &handler_chain, entries, b_tmp) {
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if (b == p) {
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LIST_REMOVE(b, entries);
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return (0);
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}
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}
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return (ENOENT); /* Handler not found. */
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}
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int
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LibAliasAttachHandlers(struct proto_handler *_p)
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{
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int i, error;
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LIBALIAS_WLOCK();
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error = -1;
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for (i = 0; 1; i++) {
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if (*((int *)&_p[i]) == EOH)
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break;
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error = _attach_handler(&_p[i]);
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if (error != 0)
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break;
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}
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LIBALIAS_WUNLOCK();
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return (error);
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}
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int
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LibAliasDetachHandlers(struct proto_handler *_p)
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{
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int i, error;
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LIBALIAS_WLOCK();
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error = -1;
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for (i = 0; 1; i++) {
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if (*((int *)&_p[i]) == EOH)
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break;
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error = _detach_handler(&_p[i]);
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if (error != 0)
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break;
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}
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LIBALIAS_WUNLOCK();
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return (error);
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}
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int
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detach_handler(struct proto_handler *_p)
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LibAliasAttachHandlers(struct proto_handler *p)
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{
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int error;
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LIBALIAS_WLOCK();
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error = -1;
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error = _detach_handler(_p);
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LIBALIAS_WUNLOCK();
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return (error);
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while (p->dir != NODIR) {
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error = attach_handler(p);
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if (error)
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return (error);
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p++;
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}
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return (0);
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}
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/* XXXGL: should be void, but no good reason to break ABI */
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int
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LibAliasDetachHandlers(struct proto_handler *p)
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{
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while (p->dir != NODIR) {
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TAILQ_REMOVE(&handler_chain, p, link);
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p++;
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}
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return (0);
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}
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int
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find_handler(int8_t dir, int8_t proto, struct libalias *la, __unused struct ip *pip,
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find_handler(int8_t dir, int8_t proto, struct libalias *la, struct ip *ip,
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struct alias_data *ad)
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{
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struct proto_handler *p;
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int error;
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LIBALIAS_RLOCK();
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error = ENOENT;
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LIST_FOREACH(p, &handler_chain, entries) {
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if ((p->dir & dir) && (p->proto & proto))
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if (p->fingerprint(la, ad) == 0) {
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error = p->protohandler(la, pip, ad);
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break;
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}
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}
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LIBALIAS_RUNLOCK();
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return (error);
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TAILQ_FOREACH(p, &handler_chain, link)
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if ((p->dir & dir) && (p->proto & proto) &&
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p->fingerprint(la, ad) == 0)
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return (p->protohandler(la, ip, ad));
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return (ENOENT);
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}
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struct proto_handler *
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first_handler(void)
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{
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return (LIST_FIRST(&handler_chain));
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return (TAILQ_FIRST(&handler_chain));
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}
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#ifndef _KERNEL
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/* Dll manipulation code - this code is not thread safe... */
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SLIST_HEAD(dll_chain, dll) dll_chain = SLIST_HEAD_INITIALIZER(dll_chain);
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int
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attach_dll(struct dll *p)
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{
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@ -45,14 +45,15 @@ MALLOC_DECLARE(M_ALIAS);
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#endif
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#endif
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/* Packet flow direction. */
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#define IN 1
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#define OUT 2
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/* Packet flow direction flags. */
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#define IN 0x0001
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#define OUT 0x0002
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#define NODIR 0x4000
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/* Working protocol. */
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#define IP 1
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#define TCP 2
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#define UDP 4
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/* Working protocol flags. */
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#define IP 0x01
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#define TCP 0x02
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#define UDP 0x04
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/*
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* Data passed to protocol handler module, it must be filled
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@ -81,18 +82,15 @@ struct proto_handler {
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/* Aliasing * function. */
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int (*protohandler)(struct libalias *, struct ip *,
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struct alias_data *);
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LIST_ENTRY(proto_handler) entries;
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}
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;
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TAILQ_ENTRY(proto_handler) link;
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};
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/* End of handlers. */
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#define EOH -1
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#define EOH .dir = NODIR
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/* Functions used with protocol handlers. */
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void handler_chain_init(void);
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void handler_chain_destroy(void);
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int LibAliasAttachHandlers(struct proto_handler *);
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int LibAliasDetachHandlers(struct proto_handler *);
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int detach_handler(struct proto_handler *);
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int find_handler(int8_t, int8_t, struct libalias *, struct ip *,
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struct alias_data *);
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struct proto_handler *first_handler(void);
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@ -25,7 +25,7 @@
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.\"
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.\" $FreeBSD$
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.\"
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.Dd July 4, 2011
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.Dd December 25, 2013
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.Dt LIBALIAS 3
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.Os
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.Sh NAME
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@ -1103,7 +1103,7 @@ struct proto_handler {
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struct ip *pip, struct alias_data *ah);
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int (*protohandler)(struct libalias *la,
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struct ip *pip, struct alias_data *ah);
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LIST_ENTRY(proto_handler) entries;
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TAILQ_ENTRY(proto_handler) link;
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};
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.Ed
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.Pp
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@ -1262,8 +1262,16 @@ Here we analyse some parts of that module.
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From
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.Pa alias_dummy.c :
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.Bd -literal
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struct proto_handler handlers [] = {{666, IN|OUT, UDP|TCP,
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&fingerprint, &protohandler}};
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struct proto_handler handlers[] = {
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{
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.pri = 666,
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.dir = IN|OUT,
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.proto = UDP|TCP,
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.fingerprint = fingerprint,
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.protohandler= protohandler,
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},
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{ EOH }
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};
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.Ed
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.Pp
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The variable
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@ -1299,12 +1307,10 @@ mod_handler(module_t mod, int type, void *data)
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switch (type) {
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case MOD_LOAD:
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error = 0;
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attach_handlers(handlers);
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error = LibAliasAttachHandlers(handlers);
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break;
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case MOD_UNLOAD:
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error = 0;
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detach_handlers(handlers;
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error = LibAliasDetachHandlers(handlers);
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break;
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default:
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error = EINVAL;
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@ -1315,9 +1321,9 @@ mod_handler(module_t mod, int type, void *data)
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When running as KLD,
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.Fn mod_handler
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registers/deregisters the module using
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.Fn attach_handlers
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.Fn LibAliasAttachHandlers
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and
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.Fn detach_handlers ,
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.Fn LibAliasDetachHandlers ,
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respectively.
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.Pp
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Every module must contain at least 2 functions: one fingerprint
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