![Daniel Borkmann](/assets/img/avatar_default.png)
This work adds a generalization of the ingress qdisc as a qdisc holding only classifiers. The clsact qdisc works on ingress, but also on egress. In both cases, it's execution happens without taking the qdisc lock, and the main difference for the egress part compared to prior version of [1] is that this can be applied with _any_ underlying real egress qdisc (also classless ones). Besides solving the use-case of [1], that is, allowing for more programmability on assigning skb->priority for the mqprio case that is supported by most popular 10G+ NICs, it also opens up a lot more flexibility for other tc applications. The main work on classification can already be done at clsact egress time if the use-case allows and state stored for later retrieval f.e. again in skb->priority with major/minors (which is checked by most classful qdiscs before consulting tc_classify()) and/or in other skb fields like skb->tc_index for some light-weight post-processing to get to the eventual classid in case of a classful qdisc. Another use case is that the clsact egress part allows to have a central egress counterpart to the ingress classifiers, so that classifiers can easily share state (e.g. in cls_bpf via eBPF maps) for ingress and egress. Currently, default setups like mq + pfifo_fast would require for this to use, for example, prio qdisc instead (to get a tc_classify() run) and to duplicate the egress classifier for each queue. With clsact, it allows for leaving the setup as is, it can additionally assign skb->priority to put the skb in one of pfifo_fast's bands and it can share state with maps. Moreover, we can access the skb's dst entry (f.e. to retrieve tclassid) w/o the need to perform a skb_dst_force() to hold on to it any longer. In lwt case, we can also use this facility to setup dst metadata via cls_bpf (bpf_skb_set_tunnel_key()) without needing a real egress qdisc just for that (case of IFF_NO_QUEUE devices, for example). The realization can be done without any changes to the scheduler core framework. All it takes is that we have two a-priori defined minors/child classes, where we can mux between ingress and egress classifier list (dev->ingress_cl_list and dev->egress_cl_list, latter stored close to dev->_tx to avoid extra cacheline miss for moderate loads). The egress part is a bit similar modelled to handle_ing() and patched to a noop in case the functionality is not used. Both handlers are now called sch_handle_ingress() and sch_handle_egress(), code sharing among the two doesn't seem practical as there are various minor differences in both paths, so that making them conditional in a single handler would rather slow things down. Full compatibility to ingress qdisc is provided as well. Since both piggyback on TC_H_CLSACT, only one of them (ingress/clsact) can exist per netdevice, and thus ingress qdisc specific behaviour can be retained for user space. This means, either a user does 'tc qdisc add dev foo ingress' and configures ingress qdisc as usual, or the 'tc qdisc add dev foo clsact' alternative, where both, ingress and egress classifier can be configured as in the below example. ingress qdisc supports attaching classifier to any minor number whereas clsact has two fixed minors for muxing between the lists, therefore to not break user space setups, they are better done as two separate qdiscs. I decided to extend the sch_ingress module with clsact functionality so that commonly used code can be reused, the module is being aliased with sch_clsact so that it can be auto-loaded properly. Alternative would have been to add a flag when initializing ingress to alter its behaviour plus aliasing to a different name (as it's more than just ingress). However, the first would end up, based on the flag, choosing the new/old behaviour by calling different function implementations to handle each anyway, the latter would require to register ingress qdisc once again under different alias. So, this really begs to provide a minimal, cleaner approach to have Qdisc_ops and Qdisc_class_ops by its own that share callbacks used by both. Example, adding qdisc: # tc qdisc add dev foo clsact # tc qdisc show dev foo qdisc mq 0: root qdisc pfifo_fast 0: parent :1 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1 qdisc pfifo_fast 0: parent :2 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1 qdisc pfifo_fast 0: parent :3 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1 qdisc pfifo_fast 0: parent :4 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1 qdisc clsact ffff: parent ffff:fff1 Adding filters (deleting, etc works analogous by specifying ingress/egress): # tc filter add dev foo ingress bpf da obj bar.o sec ingress # tc filter add dev foo egress bpf da obj bar.o sec egress # tc filter show dev foo ingress filter protocol all pref 49152 bpf filter protocol all pref 49152 bpf handle 0x1 bar.o:[ingress] direct-action # tc filter show dev foo egress filter protocol all pref 49152 bpf filter protocol all pref 49152 bpf handle 0x1 bar.o:[egress] direct-action A 'tc filter show dev foo' or 'tc filter show dev foo parent ffff:' will show an empty list for clsact. Either using the parent names (ingress/egress) or specifying the full major/minor will then show the related filter lists. Prior work on a mqprio prequeue() facility [1] was done mainly by John Fastabend. [1] http://patchwork.ozlabs.org/patch/512949/ Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: John Fastabend <john.r.fastabend@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
550 lines
12 KiB
C
550 lines
12 KiB
C
/*
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* Berkeley Packet Filter based traffic classifier
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*
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* Might be used to classify traffic through flexible, user-defined and
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* possibly JIT-ed BPF filters for traffic control as an alternative to
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* ematches.
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*
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* (C) 2013 Daniel Borkmann <dborkman@redhat.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/skbuff.h>
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#include <linux/filter.h>
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#include <linux/bpf.h>
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#include <net/rtnetlink.h>
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#include <net/pkt_cls.h>
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#include <net/sock.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Daniel Borkmann <dborkman@redhat.com>");
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MODULE_DESCRIPTION("TC BPF based classifier");
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#define CLS_BPF_NAME_LEN 256
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struct cls_bpf_head {
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struct list_head plist;
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u32 hgen;
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struct rcu_head rcu;
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};
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struct cls_bpf_prog {
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struct bpf_prog *filter;
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struct list_head link;
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struct tcf_result res;
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bool exts_integrated;
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struct tcf_exts exts;
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u32 handle;
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union {
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u32 bpf_fd;
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u16 bpf_num_ops;
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};
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struct sock_filter *bpf_ops;
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const char *bpf_name;
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struct tcf_proto *tp;
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struct rcu_head rcu;
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};
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static const struct nla_policy bpf_policy[TCA_BPF_MAX + 1] = {
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[TCA_BPF_CLASSID] = { .type = NLA_U32 },
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[TCA_BPF_FLAGS] = { .type = NLA_U32 },
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[TCA_BPF_FD] = { .type = NLA_U32 },
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[TCA_BPF_NAME] = { .type = NLA_NUL_STRING, .len = CLS_BPF_NAME_LEN },
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[TCA_BPF_OPS_LEN] = { .type = NLA_U16 },
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[TCA_BPF_OPS] = { .type = NLA_BINARY,
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.len = sizeof(struct sock_filter) * BPF_MAXINSNS },
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};
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static int cls_bpf_exec_opcode(int code)
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{
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switch (code) {
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case TC_ACT_OK:
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case TC_ACT_SHOT:
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case TC_ACT_STOLEN:
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case TC_ACT_REDIRECT:
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case TC_ACT_UNSPEC:
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return code;
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default:
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return TC_ACT_UNSPEC;
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}
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}
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static int cls_bpf_classify(struct sk_buff *skb, const struct tcf_proto *tp,
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struct tcf_result *res)
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{
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struct cls_bpf_head *head = rcu_dereference_bh(tp->root);
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bool at_ingress = skb_at_tc_ingress(skb);
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struct cls_bpf_prog *prog;
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int ret = -1;
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if (unlikely(!skb_mac_header_was_set(skb)))
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return -1;
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/* Needed here for accessing maps. */
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rcu_read_lock();
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list_for_each_entry_rcu(prog, &head->plist, link) {
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int filter_res;
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qdisc_skb_cb(skb)->tc_classid = prog->res.classid;
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if (at_ingress) {
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/* It is safe to push/pull even if skb_shared() */
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__skb_push(skb, skb->mac_len);
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filter_res = BPF_PROG_RUN(prog->filter, skb);
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__skb_pull(skb, skb->mac_len);
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} else {
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filter_res = BPF_PROG_RUN(prog->filter, skb);
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}
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if (prog->exts_integrated) {
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res->class = prog->res.class;
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res->classid = qdisc_skb_cb(skb)->tc_classid;
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ret = cls_bpf_exec_opcode(filter_res);
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if (ret == TC_ACT_UNSPEC)
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continue;
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break;
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}
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if (filter_res == 0)
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continue;
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*res = prog->res;
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if (filter_res != -1)
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res->classid = filter_res;
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ret = tcf_exts_exec(skb, &prog->exts, res);
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if (ret < 0)
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continue;
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break;
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}
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rcu_read_unlock();
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return ret;
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}
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static bool cls_bpf_is_ebpf(const struct cls_bpf_prog *prog)
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{
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return !prog->bpf_ops;
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}
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static int cls_bpf_init(struct tcf_proto *tp)
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{
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struct cls_bpf_head *head;
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head = kzalloc(sizeof(*head), GFP_KERNEL);
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if (head == NULL)
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return -ENOBUFS;
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INIT_LIST_HEAD_RCU(&head->plist);
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rcu_assign_pointer(tp->root, head);
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return 0;
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}
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static void cls_bpf_delete_prog(struct tcf_proto *tp, struct cls_bpf_prog *prog)
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{
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tcf_exts_destroy(&prog->exts);
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if (cls_bpf_is_ebpf(prog))
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bpf_prog_put(prog->filter);
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else
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bpf_prog_destroy(prog->filter);
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kfree(prog->bpf_name);
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kfree(prog->bpf_ops);
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kfree(prog);
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}
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static void __cls_bpf_delete_prog(struct rcu_head *rcu)
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{
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struct cls_bpf_prog *prog = container_of(rcu, struct cls_bpf_prog, rcu);
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cls_bpf_delete_prog(prog->tp, prog);
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}
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static int cls_bpf_delete(struct tcf_proto *tp, unsigned long arg)
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{
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struct cls_bpf_prog *prog = (struct cls_bpf_prog *) arg;
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list_del_rcu(&prog->link);
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tcf_unbind_filter(tp, &prog->res);
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call_rcu(&prog->rcu, __cls_bpf_delete_prog);
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return 0;
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}
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static bool cls_bpf_destroy(struct tcf_proto *tp, bool force)
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{
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struct cls_bpf_head *head = rtnl_dereference(tp->root);
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struct cls_bpf_prog *prog, *tmp;
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if (!force && !list_empty(&head->plist))
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return false;
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list_for_each_entry_safe(prog, tmp, &head->plist, link) {
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list_del_rcu(&prog->link);
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tcf_unbind_filter(tp, &prog->res);
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call_rcu(&prog->rcu, __cls_bpf_delete_prog);
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}
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RCU_INIT_POINTER(tp->root, NULL);
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kfree_rcu(head, rcu);
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return true;
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}
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static unsigned long cls_bpf_get(struct tcf_proto *tp, u32 handle)
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{
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struct cls_bpf_head *head = rtnl_dereference(tp->root);
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struct cls_bpf_prog *prog;
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unsigned long ret = 0UL;
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if (head == NULL)
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return 0UL;
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list_for_each_entry(prog, &head->plist, link) {
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if (prog->handle == handle) {
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ret = (unsigned long) prog;
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break;
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}
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}
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return ret;
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}
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static int cls_bpf_prog_from_ops(struct nlattr **tb, struct cls_bpf_prog *prog)
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{
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struct sock_filter *bpf_ops;
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struct sock_fprog_kern fprog_tmp;
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struct bpf_prog *fp;
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u16 bpf_size, bpf_num_ops;
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int ret;
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bpf_num_ops = nla_get_u16(tb[TCA_BPF_OPS_LEN]);
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if (bpf_num_ops > BPF_MAXINSNS || bpf_num_ops == 0)
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return -EINVAL;
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bpf_size = bpf_num_ops * sizeof(*bpf_ops);
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if (bpf_size != nla_len(tb[TCA_BPF_OPS]))
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return -EINVAL;
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bpf_ops = kzalloc(bpf_size, GFP_KERNEL);
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if (bpf_ops == NULL)
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return -ENOMEM;
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memcpy(bpf_ops, nla_data(tb[TCA_BPF_OPS]), bpf_size);
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fprog_tmp.len = bpf_num_ops;
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fprog_tmp.filter = bpf_ops;
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ret = bpf_prog_create(&fp, &fprog_tmp);
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if (ret < 0) {
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kfree(bpf_ops);
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return ret;
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}
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prog->bpf_ops = bpf_ops;
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prog->bpf_num_ops = bpf_num_ops;
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prog->bpf_name = NULL;
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prog->filter = fp;
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return 0;
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}
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static int cls_bpf_prog_from_efd(struct nlattr **tb, struct cls_bpf_prog *prog,
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const struct tcf_proto *tp)
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{
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struct bpf_prog *fp;
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char *name = NULL;
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u32 bpf_fd;
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bpf_fd = nla_get_u32(tb[TCA_BPF_FD]);
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fp = bpf_prog_get(bpf_fd);
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if (IS_ERR(fp))
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return PTR_ERR(fp);
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if (fp->type != BPF_PROG_TYPE_SCHED_CLS) {
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bpf_prog_put(fp);
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return -EINVAL;
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}
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if (tb[TCA_BPF_NAME]) {
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name = kmemdup(nla_data(tb[TCA_BPF_NAME]),
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nla_len(tb[TCA_BPF_NAME]),
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GFP_KERNEL);
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if (!name) {
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bpf_prog_put(fp);
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return -ENOMEM;
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}
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}
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prog->bpf_ops = NULL;
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prog->bpf_fd = bpf_fd;
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prog->bpf_name = name;
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prog->filter = fp;
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if (fp->dst_needed && !(tp->q->flags & TCQ_F_INGRESS))
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netif_keep_dst(qdisc_dev(tp->q));
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return 0;
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}
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static int cls_bpf_modify_existing(struct net *net, struct tcf_proto *tp,
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struct cls_bpf_prog *prog,
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unsigned long base, struct nlattr **tb,
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struct nlattr *est, bool ovr)
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{
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bool is_bpf, is_ebpf, have_exts = false;
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struct tcf_exts exts;
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int ret;
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is_bpf = tb[TCA_BPF_OPS_LEN] && tb[TCA_BPF_OPS];
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is_ebpf = tb[TCA_BPF_FD];
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if ((!is_bpf && !is_ebpf) || (is_bpf && is_ebpf))
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return -EINVAL;
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tcf_exts_init(&exts, TCA_BPF_ACT, TCA_BPF_POLICE);
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ret = tcf_exts_validate(net, tp, tb, est, &exts, ovr);
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if (ret < 0)
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return ret;
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if (tb[TCA_BPF_FLAGS]) {
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u32 bpf_flags = nla_get_u32(tb[TCA_BPF_FLAGS]);
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if (bpf_flags & ~TCA_BPF_FLAG_ACT_DIRECT) {
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tcf_exts_destroy(&exts);
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return -EINVAL;
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}
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have_exts = bpf_flags & TCA_BPF_FLAG_ACT_DIRECT;
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}
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prog->exts_integrated = have_exts;
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ret = is_bpf ? cls_bpf_prog_from_ops(tb, prog) :
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cls_bpf_prog_from_efd(tb, prog, tp);
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if (ret < 0) {
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tcf_exts_destroy(&exts);
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return ret;
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}
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if (tb[TCA_BPF_CLASSID]) {
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prog->res.classid = nla_get_u32(tb[TCA_BPF_CLASSID]);
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tcf_bind_filter(tp, &prog->res, base);
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}
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tcf_exts_change(tp, &prog->exts, &exts);
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return 0;
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}
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static u32 cls_bpf_grab_new_handle(struct tcf_proto *tp,
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struct cls_bpf_head *head)
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{
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unsigned int i = 0x80000000;
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u32 handle;
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do {
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if (++head->hgen == 0x7FFFFFFF)
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head->hgen = 1;
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} while (--i > 0 && cls_bpf_get(tp, head->hgen));
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if (unlikely(i == 0)) {
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pr_err("Insufficient number of handles\n");
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handle = 0;
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} else {
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handle = head->hgen;
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}
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return handle;
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}
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static int cls_bpf_change(struct net *net, struct sk_buff *in_skb,
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struct tcf_proto *tp, unsigned long base,
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u32 handle, struct nlattr **tca,
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unsigned long *arg, bool ovr)
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{
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struct cls_bpf_head *head = rtnl_dereference(tp->root);
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struct cls_bpf_prog *oldprog = (struct cls_bpf_prog *) *arg;
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struct nlattr *tb[TCA_BPF_MAX + 1];
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struct cls_bpf_prog *prog;
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int ret;
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if (tca[TCA_OPTIONS] == NULL)
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return -EINVAL;
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ret = nla_parse_nested(tb, TCA_BPF_MAX, tca[TCA_OPTIONS], bpf_policy);
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if (ret < 0)
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return ret;
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prog = kzalloc(sizeof(*prog), GFP_KERNEL);
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if (!prog)
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return -ENOBUFS;
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tcf_exts_init(&prog->exts, TCA_BPF_ACT, TCA_BPF_POLICE);
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if (oldprog) {
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if (handle && oldprog->handle != handle) {
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ret = -EINVAL;
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goto errout;
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}
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}
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if (handle == 0)
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prog->handle = cls_bpf_grab_new_handle(tp, head);
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else
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prog->handle = handle;
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if (prog->handle == 0) {
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ret = -EINVAL;
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goto errout;
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}
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ret = cls_bpf_modify_existing(net, tp, prog, base, tb, tca[TCA_RATE], ovr);
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if (ret < 0)
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goto errout;
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if (oldprog) {
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list_replace_rcu(&oldprog->link, &prog->link);
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tcf_unbind_filter(tp, &oldprog->res);
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call_rcu(&oldprog->rcu, __cls_bpf_delete_prog);
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} else {
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list_add_rcu(&prog->link, &head->plist);
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}
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*arg = (unsigned long) prog;
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return 0;
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errout:
|
|
kfree(prog);
|
|
|
|
return ret;
|
|
}
|
|
|
|
static int cls_bpf_dump_bpf_info(const struct cls_bpf_prog *prog,
|
|
struct sk_buff *skb)
|
|
{
|
|
struct nlattr *nla;
|
|
|
|
if (nla_put_u16(skb, TCA_BPF_OPS_LEN, prog->bpf_num_ops))
|
|
return -EMSGSIZE;
|
|
|
|
nla = nla_reserve(skb, TCA_BPF_OPS, prog->bpf_num_ops *
|
|
sizeof(struct sock_filter));
|
|
if (nla == NULL)
|
|
return -EMSGSIZE;
|
|
|
|
memcpy(nla_data(nla), prog->bpf_ops, nla_len(nla));
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int cls_bpf_dump_ebpf_info(const struct cls_bpf_prog *prog,
|
|
struct sk_buff *skb)
|
|
{
|
|
if (nla_put_u32(skb, TCA_BPF_FD, prog->bpf_fd))
|
|
return -EMSGSIZE;
|
|
|
|
if (prog->bpf_name &&
|
|
nla_put_string(skb, TCA_BPF_NAME, prog->bpf_name))
|
|
return -EMSGSIZE;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int cls_bpf_dump(struct net *net, struct tcf_proto *tp, unsigned long fh,
|
|
struct sk_buff *skb, struct tcmsg *tm)
|
|
{
|
|
struct cls_bpf_prog *prog = (struct cls_bpf_prog *) fh;
|
|
struct nlattr *nest;
|
|
u32 bpf_flags = 0;
|
|
int ret;
|
|
|
|
if (prog == NULL)
|
|
return skb->len;
|
|
|
|
tm->tcm_handle = prog->handle;
|
|
|
|
nest = nla_nest_start(skb, TCA_OPTIONS);
|
|
if (nest == NULL)
|
|
goto nla_put_failure;
|
|
|
|
if (prog->res.classid &&
|
|
nla_put_u32(skb, TCA_BPF_CLASSID, prog->res.classid))
|
|
goto nla_put_failure;
|
|
|
|
if (cls_bpf_is_ebpf(prog))
|
|
ret = cls_bpf_dump_ebpf_info(prog, skb);
|
|
else
|
|
ret = cls_bpf_dump_bpf_info(prog, skb);
|
|
if (ret)
|
|
goto nla_put_failure;
|
|
|
|
if (tcf_exts_dump(skb, &prog->exts) < 0)
|
|
goto nla_put_failure;
|
|
|
|
if (prog->exts_integrated)
|
|
bpf_flags |= TCA_BPF_FLAG_ACT_DIRECT;
|
|
if (bpf_flags && nla_put_u32(skb, TCA_BPF_FLAGS, bpf_flags))
|
|
goto nla_put_failure;
|
|
|
|
nla_nest_end(skb, nest);
|
|
|
|
if (tcf_exts_dump_stats(skb, &prog->exts) < 0)
|
|
goto nla_put_failure;
|
|
|
|
return skb->len;
|
|
|
|
nla_put_failure:
|
|
nla_nest_cancel(skb, nest);
|
|
return -1;
|
|
}
|
|
|
|
static void cls_bpf_walk(struct tcf_proto *tp, struct tcf_walker *arg)
|
|
{
|
|
struct cls_bpf_head *head = rtnl_dereference(tp->root);
|
|
struct cls_bpf_prog *prog;
|
|
|
|
list_for_each_entry(prog, &head->plist, link) {
|
|
if (arg->count < arg->skip)
|
|
goto skip;
|
|
if (arg->fn(tp, (unsigned long) prog, arg) < 0) {
|
|
arg->stop = 1;
|
|
break;
|
|
}
|
|
skip:
|
|
arg->count++;
|
|
}
|
|
}
|
|
|
|
static struct tcf_proto_ops cls_bpf_ops __read_mostly = {
|
|
.kind = "bpf",
|
|
.owner = THIS_MODULE,
|
|
.classify = cls_bpf_classify,
|
|
.init = cls_bpf_init,
|
|
.destroy = cls_bpf_destroy,
|
|
.get = cls_bpf_get,
|
|
.change = cls_bpf_change,
|
|
.delete = cls_bpf_delete,
|
|
.walk = cls_bpf_walk,
|
|
.dump = cls_bpf_dump,
|
|
};
|
|
|
|
static int __init cls_bpf_init_mod(void)
|
|
{
|
|
return register_tcf_proto_ops(&cls_bpf_ops);
|
|
}
|
|
|
|
static void __exit cls_bpf_exit_mod(void)
|
|
{
|
|
unregister_tcf_proto_ops(&cls_bpf_ops);
|
|
}
|
|
|
|
module_init(cls_bpf_init_mod);
|
|
module_exit(cls_bpf_exit_mod);
|