--- /dev/null
+/*
+ * 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);
Code Review / kvmfornfv.git / blobdiff