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c56716c69c
Multiple netfilter extensions store pointers to external data in their extension area struct. Examples: 1. Timeout policies 2. Connection tracking helpers. No references are taken for these. When a helper or timeout policy is removed, the conntrack table gets traversed and affected extensions are cleared. Conntrack entries not yet in the hashtable are referenced via a special list, the unconfirmed list. On removal of a policy or connection tracking helper, the unconfirmed list gets traversed an all entries are marked as dying, this prevents them from getting committed to the table at insertion time: core checks for dying bit, if set, the conntrack entry gets destroyed at confirm time. The disadvantage is that each new conntrack has to be added to the percpu unconfirmed list, and each insertion needs to remove it from this list. The list is only ever needed when a policy or helper is removed -- a rare occurrence. Add a generation ID count: Instead of adding to the list and then traversing that list on policy/helper removal, increment a counter that is stored in the extension area. For unconfirmed conntracks, the extension has the genid valid at ct allocation time. Removal of a helper/policy etc. increments the counter. At confirmation time, validate that ext->genid == global_id. If the stored number is not the same, do not allow the conntrack insertion, just like as if a confirmed-list traversal would have flagged the entry as dying. After insertion, the genid is no longer relevant (conntrack entries are now reachable via the conntrack table iterators and is set to 0. This allows removal of the percpu unconfirmed list. Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
79 lines
1.8 KiB
C
79 lines
1.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _NF_CONNTRACK_EXTEND_H
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#define _NF_CONNTRACK_EXTEND_H
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#include <linux/slab.h>
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#include <net/netfilter/nf_conntrack.h>
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enum nf_ct_ext_id {
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NF_CT_EXT_HELPER,
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#if IS_ENABLED(CONFIG_NF_NAT)
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NF_CT_EXT_NAT,
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#endif
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NF_CT_EXT_SEQADJ,
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NF_CT_EXT_ACCT,
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#ifdef CONFIG_NF_CONNTRACK_EVENTS
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NF_CT_EXT_ECACHE,
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#endif
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#ifdef CONFIG_NF_CONNTRACK_TIMESTAMP
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NF_CT_EXT_TSTAMP,
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#endif
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#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
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NF_CT_EXT_TIMEOUT,
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#endif
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#ifdef CONFIG_NF_CONNTRACK_LABELS
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NF_CT_EXT_LABELS,
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#endif
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#if IS_ENABLED(CONFIG_NETFILTER_SYNPROXY)
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NF_CT_EXT_SYNPROXY,
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#endif
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#if IS_ENABLED(CONFIG_NET_ACT_CT)
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NF_CT_EXT_ACT_CT,
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#endif
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NF_CT_EXT_NUM,
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};
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/* Extensions: optional stuff which isn't permanently in struct. */
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struct nf_ct_ext {
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u8 offset[NF_CT_EXT_NUM];
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u8 len;
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unsigned int gen_id;
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char data[] __aligned(8);
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};
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static inline bool __nf_ct_ext_exist(const struct nf_ct_ext *ext, u8 id)
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{
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return !!ext->offset[id];
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}
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static inline bool nf_ct_ext_exist(const struct nf_conn *ct, u8 id)
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{
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return (ct->ext && __nf_ct_ext_exist(ct->ext, id));
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}
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void *__nf_ct_ext_find(const struct nf_ct_ext *ext, u8 id);
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static inline void *nf_ct_ext_find(const struct nf_conn *ct, u8 id)
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{
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struct nf_ct_ext *ext = ct->ext;
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if (!ext || !__nf_ct_ext_exist(ext, id))
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return NULL;
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if (unlikely(ext->gen_id))
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return __nf_ct_ext_find(ext, id);
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return (void *)ct->ext + ct->ext->offset[id];
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}
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/* Add this type, returns pointer to data or NULL. */
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void *nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp);
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/* ext genid. if ext->id != ext_genid, extensions cannot be used
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* anymore unless conntrack has CONFIRMED bit set.
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*/
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extern atomic_t nf_conntrack_ext_genid;
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void nf_ct_ext_bump_genid(void);
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#endif /* _NF_CONNTRACK_EXTEND_H */
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