diff options
Diffstat (limited to 'kernel/net/sched/ematch.c')
| -rw-r--r-- | kernel/net/sched/ematch.c | 549 |
1 files changed, 549 insertions, 0 deletions
diff --git a/kernel/net/sched/ematch.c b/kernel/net/sched/ematch.c new file mode 100644 index 000000000..fbb7ebfc5 --- /dev/null +++ b/kernel/net/sched/ematch.c @@ -0,0 +1,549 @@ +/* + * net/sched/ematch.c Extended Match API + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + * + * Authors: Thomas Graf <tgraf@suug.ch> + * + * ========================================================================== + * + * An extended match (ematch) is a small classification tool not worth + * writing a full classifier for. Ematches can be interconnected to form + * a logic expression and get attached to classifiers to extend their + * functionatlity. + * + * The userspace part transforms the logic expressions into an array + * consisting of multiple sequences of interconnected ematches separated + * by markers. Precedence is implemented by a special ematch kind + * referencing a sequence beyond the marker of the current sequence + * causing the current position in the sequence to be pushed onto a stack + * to allow the current position to be overwritten by the position referenced + * in the special ematch. Matching continues in the new sequence until a + * marker is reached causing the position to be restored from the stack. + * + * Example: + * A AND (B1 OR B2) AND C AND D + * + * ------->-PUSH------- + * -->-- / -->-- \ -->-- + * / \ / / \ \ / \ + * +-------+-------+-------+-------+-------+--------+ + * | A AND | B AND | C AND | D END | B1 OR | B2 END | + * +-------+-------+-------+-------+-------+--------+ + * \ / + * --------<-POP--------- + * + * where B is a virtual ematch referencing to sequence starting with B1. + * + * ========================================================================== + * + * How to write an ematch in 60 seconds + * ------------------------------------ + * + * 1) Provide a matcher function: + * static int my_match(struct sk_buff *skb, struct tcf_ematch *m, + * struct tcf_pkt_info *info) + * { + * struct mydata *d = (struct mydata *) m->data; + * + * if (...matching goes here...) + * return 1; + * else + * return 0; + * } + * + * 2) Fill out a struct tcf_ematch_ops: + * static struct tcf_ematch_ops my_ops = { + * .kind = unique id, + * .datalen = sizeof(struct mydata), + * .match = my_match, + * .owner = THIS_MODULE, + * }; + * + * 3) Register/Unregister your ematch: + * static int __init init_my_ematch(void) + * { + * return tcf_em_register(&my_ops); + * } + * + * static void __exit exit_my_ematch(void) + * { + * tcf_em_unregister(&my_ops); + * } + * + * module_init(init_my_ematch); + * module_exit(exit_my_ematch); + * + * 4) By now you should have two more seconds left, barely enough to + * open up a beer to watch the compilation going. + */ + +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/types.h> +#include <linux/kernel.h> +#include <linux/errno.h> +#include <linux/rtnetlink.h> +#include <linux/skbuff.h> +#include <net/pkt_cls.h> + +static LIST_HEAD(ematch_ops); +static DEFINE_RWLOCK(ematch_mod_lock); + +static struct tcf_ematch_ops *tcf_em_lookup(u16 kind) +{ + struct tcf_ematch_ops *e = NULL; + + read_lock(&ematch_mod_lock); + list_for_each_entry(e, &ematch_ops, link) { + if (kind == e->kind) { + if (!try_module_get(e->owner)) + e = NULL; + read_unlock(&ematch_mod_lock); + return e; + } + } + read_unlock(&ematch_mod_lock); + + return NULL; +} + +/** + * tcf_em_register - register an extended match + * + * @ops: ematch operations lookup table + * + * This function must be called by ematches to announce their presence. + * The given @ops must have kind set to a unique identifier and the + * callback match() must be implemented. All other callbacks are optional + * and a fallback implementation is used instead. + * + * Returns -EEXISTS if an ematch of the same kind has already registered. + */ +int tcf_em_register(struct tcf_ematch_ops *ops) +{ + int err = -EEXIST; + struct tcf_ematch_ops *e; + + if (ops->match == NULL) + return -EINVAL; + + write_lock(&ematch_mod_lock); + list_for_each_entry(e, &ematch_ops, link) + if (ops->kind == e->kind) + goto errout; + + list_add_tail(&ops->link, &ematch_ops); + err = 0; +errout: + write_unlock(&ematch_mod_lock); + return err; +} +EXPORT_SYMBOL(tcf_em_register); + +/** + * tcf_em_unregister - unregster and extended match + * + * @ops: ematch operations lookup table + * + * This function must be called by ematches to announce their disappearance + * for examples when the module gets unloaded. The @ops parameter must be + * the same as the one used for registration. + * + * Returns -ENOENT if no matching ematch was found. + */ +void tcf_em_unregister(struct tcf_ematch_ops *ops) +{ + write_lock(&ematch_mod_lock); + list_del(&ops->link); + write_unlock(&ematch_mod_lock); +} +EXPORT_SYMBOL(tcf_em_unregister); + +static inline struct tcf_ematch *tcf_em_get_match(struct tcf_ematch_tree *tree, + int index) +{ + return &tree->matches[index]; +} + + +static int tcf_em_validate(struct tcf_proto *tp, + struct tcf_ematch_tree_hdr *tree_hdr, + struct tcf_ematch *em, struct nlattr *nla, int idx) +{ + int err = -EINVAL; + struct tcf_ematch_hdr *em_hdr = nla_data(nla); + int data_len = nla_len(nla) - sizeof(*em_hdr); + void *data = (void *) em_hdr + sizeof(*em_hdr); + struct net *net = dev_net(qdisc_dev(tp->q)); + + if (!TCF_EM_REL_VALID(em_hdr->flags)) + goto errout; + + if (em_hdr->kind == TCF_EM_CONTAINER) { + /* Special ematch called "container", carries an index + * referencing an external ematch sequence. + */ + u32 ref; + + if (data_len < sizeof(ref)) + goto errout; + ref = *(u32 *) data; + + if (ref >= tree_hdr->nmatches) + goto errout; + + /* We do not allow backward jumps to avoid loops and jumps + * to our own position are of course illegal. + */ + if (ref <= idx) + goto errout; + + + em->data = ref; + } else { + /* Note: This lookup will increase the module refcnt + * of the ematch module referenced. In case of a failure, + * a destroy function is called by the underlying layer + * which automatically releases the reference again, therefore + * the module MUST not be given back under any circumstances + * here. Be aware, the destroy function assumes that the + * module is held if the ops field is non zero. + */ + em->ops = tcf_em_lookup(em_hdr->kind); + + if (em->ops == NULL) { + err = -ENOENT; +#ifdef CONFIG_MODULES + __rtnl_unlock(); + request_module("ematch-kind-%u", em_hdr->kind); + rtnl_lock(); + em->ops = tcf_em_lookup(em_hdr->kind); + if (em->ops) { + /* We dropped the RTNL mutex in order to + * perform the module load. Tell the caller + * to replay the request. + */ + module_put(em->ops->owner); + em->ops = NULL; + err = -EAGAIN; + } +#endif + goto errout; + } + + /* ematch module provides expected length of data, so we + * can do a basic sanity check. + */ + if (em->ops->datalen && data_len < em->ops->datalen) + goto errout; + + if (em->ops->change) { + err = em->ops->change(net, data, data_len, em); + if (err < 0) + goto errout; + } else if (data_len > 0) { + /* ematch module doesn't provide an own change + * procedure and expects us to allocate and copy + * the ematch data. + * + * TCF_EM_SIMPLE may be specified stating that the + * data only consists of a u32 integer and the module + * does not expected a memory reference but rather + * the value carried. + */ + if (em_hdr->flags & TCF_EM_SIMPLE) { + if (data_len < sizeof(u32)) + goto errout; + em->data = *(u32 *) data; + } else { + void *v = kmemdup(data, data_len, GFP_KERNEL); + if (v == NULL) { + err = -ENOBUFS; + goto errout; + } + em->data = (unsigned long) v; + } + } + } + + em->matchid = em_hdr->matchid; + em->flags = em_hdr->flags; + em->datalen = data_len; + em->net = net; + + err = 0; +errout: + return err; +} + +static const struct nla_policy em_policy[TCA_EMATCH_TREE_MAX + 1] = { + [TCA_EMATCH_TREE_HDR] = { .len = sizeof(struct tcf_ematch_tree_hdr) }, + [TCA_EMATCH_TREE_LIST] = { .type = NLA_NESTED }, +}; + +/** + * tcf_em_tree_validate - validate ematch config TLV and build ematch tree + * + * @tp: classifier kind handle + * @nla: ematch tree configuration TLV + * @tree: destination ematch tree variable to store the resulting + * ematch tree. + * + * This function validates the given configuration TLV @nla and builds an + * ematch tree in @tree. The resulting tree must later be copied into + * the private classifier data using tcf_em_tree_change(). You MUST NOT + * provide the ematch tree variable of the private classifier data directly, + * the changes would not be locked properly. + * + * Returns a negative error code if the configuration TLV contains errors. + */ +int tcf_em_tree_validate(struct tcf_proto *tp, struct nlattr *nla, + struct tcf_ematch_tree *tree) +{ + int idx, list_len, matches_len, err; + struct nlattr *tb[TCA_EMATCH_TREE_MAX + 1]; + struct nlattr *rt_match, *rt_hdr, *rt_list; + struct tcf_ematch_tree_hdr *tree_hdr; + struct tcf_ematch *em; + + memset(tree, 0, sizeof(*tree)); + if (!nla) + return 0; + + err = nla_parse_nested(tb, TCA_EMATCH_TREE_MAX, nla, em_policy); + if (err < 0) + goto errout; + + err = -EINVAL; + rt_hdr = tb[TCA_EMATCH_TREE_HDR]; + rt_list = tb[TCA_EMATCH_TREE_LIST]; + + if (rt_hdr == NULL || rt_list == NULL) + goto errout; + + tree_hdr = nla_data(rt_hdr); + memcpy(&tree->hdr, tree_hdr, sizeof(*tree_hdr)); + + rt_match = nla_data(rt_list); + list_len = nla_len(rt_list); + matches_len = tree_hdr->nmatches * sizeof(*em); + + tree->matches = kzalloc(matches_len, GFP_KERNEL); + if (tree->matches == NULL) + goto errout; + + /* We do not use nla_parse_nested here because the maximum + * number of attributes is unknown. This saves us the allocation + * for a tb buffer which would serve no purpose at all. + * + * The array of rt attributes is parsed in the order as they are + * provided, their type must be incremental from 1 to n. Even + * if it does not serve any real purpose, a failure of sticking + * to this policy will result in parsing failure. + */ + for (idx = 0; nla_ok(rt_match, list_len); idx++) { + err = -EINVAL; + + if (rt_match->nla_type != (idx + 1)) + goto errout_abort; + + if (idx >= tree_hdr->nmatches) + goto errout_abort; + + if (nla_len(rt_match) < sizeof(struct tcf_ematch_hdr)) + goto errout_abort; + + em = tcf_em_get_match(tree, idx); + + err = tcf_em_validate(tp, tree_hdr, em, rt_match, idx); + if (err < 0) + goto errout_abort; + + rt_match = nla_next(rt_match, &list_len); + } + + /* Check if the number of matches provided by userspace actually + * complies with the array of matches. The number was used for + * the validation of references and a mismatch could lead to + * undefined references during the matching process. + */ + if (idx != tree_hdr->nmatches) { + err = -EINVAL; + goto errout_abort; + } + + err = 0; +errout: + return err; + +errout_abort: + tcf_em_tree_destroy(tree); + return err; +} +EXPORT_SYMBOL(tcf_em_tree_validate); + +/** + * tcf_em_tree_destroy - destroy an ematch tree + * + * @tp: classifier kind handle + * @tree: ematch tree to be deleted + * + * This functions destroys an ematch tree previously created by + * tcf_em_tree_validate()/tcf_em_tree_change(). You must ensure that + * the ematch tree is not in use before calling this function. + */ +void tcf_em_tree_destroy(struct tcf_ematch_tree *tree) +{ + int i; + + if (tree->matches == NULL) + return; + + for (i = 0; i < tree->hdr.nmatches; i++) { + struct tcf_ematch *em = tcf_em_get_match(tree, i); + + if (em->ops) { + if (em->ops->destroy) + em->ops->destroy(em); + else if (!tcf_em_is_simple(em)) + kfree((void *) em->data); + module_put(em->ops->owner); + } + } + + tree->hdr.nmatches = 0; + kfree(tree->matches); + tree->matches = NULL; +} +EXPORT_SYMBOL(tcf_em_tree_destroy); + +/** + * tcf_em_tree_dump - dump ematch tree into a rtnl message + * + * @skb: skb holding the rtnl message + * @t: ematch tree to be dumped + * @tlv: TLV type to be used to encapsulate the tree + * + * This function dumps a ematch tree into a rtnl message. It is valid to + * call this function while the ematch tree is in use. + * + * Returns -1 if the skb tailroom is insufficient. + */ +int tcf_em_tree_dump(struct sk_buff *skb, struct tcf_ematch_tree *tree, int tlv) +{ + int i; + u8 *tail; + struct nlattr *top_start; + struct nlattr *list_start; + + top_start = nla_nest_start(skb, tlv); + if (top_start == NULL) + goto nla_put_failure; + + if (nla_put(skb, TCA_EMATCH_TREE_HDR, sizeof(tree->hdr), &tree->hdr)) + goto nla_put_failure; + + list_start = nla_nest_start(skb, TCA_EMATCH_TREE_LIST); + if (list_start == NULL) + goto nla_put_failure; + + tail = skb_tail_pointer(skb); + for (i = 0; i < tree->hdr.nmatches; i++) { + struct nlattr *match_start = (struct nlattr *)tail; + struct tcf_ematch *em = tcf_em_get_match(tree, i); + struct tcf_ematch_hdr em_hdr = { + .kind = em->ops ? em->ops->kind : TCF_EM_CONTAINER, + .matchid = em->matchid, + .flags = em->flags + }; + + if (nla_put(skb, i + 1, sizeof(em_hdr), &em_hdr)) + goto nla_put_failure; + + if (em->ops && em->ops->dump) { + if (em->ops->dump(skb, em) < 0) + goto nla_put_failure; + } else if (tcf_em_is_container(em) || tcf_em_is_simple(em)) { + u32 u = em->data; + nla_put_nohdr(skb, sizeof(u), &u); + } else if (em->datalen > 0) + nla_put_nohdr(skb, em->datalen, (void *) em->data); + + tail = skb_tail_pointer(skb); + match_start->nla_len = tail - (u8 *)match_start; + } + + nla_nest_end(skb, list_start); + nla_nest_end(skb, top_start); + + return 0; + +nla_put_failure: + return -1; +} +EXPORT_SYMBOL(tcf_em_tree_dump); + +static inline int tcf_em_match(struct sk_buff *skb, struct tcf_ematch *em, + struct tcf_pkt_info *info) +{ + int r = em->ops->match(skb, em, info); + + return tcf_em_is_inverted(em) ? !r : r; +} + +/* Do not use this function directly, use tcf_em_tree_match instead */ +int __tcf_em_tree_match(struct sk_buff *skb, struct tcf_ematch_tree *tree, + struct tcf_pkt_info *info) +{ + int stackp = 0, match_idx = 0, res = 0; + struct tcf_ematch *cur_match; + int stack[CONFIG_NET_EMATCH_STACK]; + +proceed: + while (match_idx < tree->hdr.nmatches) { + cur_match = tcf_em_get_match(tree, match_idx); + + if (tcf_em_is_container(cur_match)) { + if (unlikely(stackp >= CONFIG_NET_EMATCH_STACK)) + goto stack_overflow; + + stack[stackp++] = match_idx; + match_idx = cur_match->data; + goto proceed; + } + + res = tcf_em_match(skb, cur_match, info); + + if (tcf_em_early_end(cur_match, res)) + break; + + match_idx++; + } + +pop_stack: + if (stackp > 0) { + match_idx = stack[--stackp]; + cur_match = tcf_em_get_match(tree, match_idx); + + if (tcf_em_is_inverted(cur_match)) + res = !res; + + if (tcf_em_early_end(cur_match, res)) { + goto pop_stack; + } else { + match_idx++; + goto proceed; + } + } + + return res; + +stack_overflow: + net_warn_ratelimited("tc ematch: local stack overflow, increase NET_EMATCH_STACK\n"); + return -1; +} +EXPORT_SYMBOL(__tcf_em_tree_match); |