cregit-Linux how code gets into the kernel

Release 4.8 net/netfilter/nf_nat_core.c

Directory: net/netfilter
/*
 * (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
 * (C) 2011 Patrick McHardy <kaber@trash.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/skbuff.h>
#include <linux/gfp.h>
#include <net/xfrm.h>
#include <linux/jhash.h>
#include <linux/rtnetlink.h>

#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_l3proto.h>
#include <net/netfilter/nf_nat_l4proto.h>
#include <net/netfilter/nf_nat_core.h>
#include <net/netfilter/nf_nat_helper.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_seqadj.h>
#include <net/netfilter/nf_conntrack_l3proto.h>
#include <net/netfilter/nf_conntrack_zones.h>
#include <linux/netfilter/nf_nat.h>

static DEFINE_MUTEX(nf_nat_proto_mutex);
static const struct nf_nat_l3proto __rcu *nf_nat_l3protos[NFPROTO_NUMPROTO]
						
__read_mostly;
static const struct nf_nat_l4proto __rcu **nf_nat_l4protos[NFPROTO_NUMPROTO]
						
__read_mostly;


struct nf_nat_conn_key {
	
const struct net *net;
	
const struct nf_conntrack_tuple *tuple;
	
const struct nf_conntrack_zone *zone;
};


static struct rhashtable nf_nat_bysource_table;


inline const struct nf_nat_l3proto * __nf_nat_l3proto_find(u8 family) { return rcu_dereference(nf_nat_l3protos[family]); }

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Total21100.00%4100.00%


inline const struct nf_nat_l4proto * __nf_nat_l4proto_find(u8 family, u8 protonum) { return rcu_dereference(nf_nat_l4protos[family][protonum]); }

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EXPORT_SYMBOL_GPL(__nf_nat_l4proto_find); #ifdef CONFIG_XFRM
static void __nf_nat_decode_session(struct sk_buff *skb, struct flowi *fl) { const struct nf_nat_l3proto *l3proto; const struct nf_conn *ct; enum ip_conntrack_info ctinfo; enum ip_conntrack_dir dir; unsigned long statusbit; u8 family; ct = nf_ct_get(skb, &ctinfo); if (ct == NULL) return; family = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.l3num; rcu_read_lock(); l3proto = __nf_nat_l3proto_find(family); if (l3proto == NULL) goto out; dir = CTINFO2DIR(ctinfo); if (dir == IP_CT_DIR_ORIGINAL) statusbit = IPS_DST_NAT; else statusbit = IPS_SRC_NAT; l3proto->decode_session(skb, ct, dir, statusbit, fl); out: rcu_read_unlock(); }

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Total136100.00%4100.00%


int nf_xfrm_me_harder(struct net *net, struct sk_buff *skb, unsigned int family) { struct flowi fl; unsigned int hh_len; struct dst_entry *dst; int err; err = xfrm_decode_session(skb, &fl, family); if (err < 0) return err; dst = skb_dst(skb); if (dst->xfrm) dst = ((struct xfrm_dst *)dst)->route; dst_hold(dst); dst = xfrm_lookup(net, dst, &fl, skb->sk, 0); if (IS_ERR(dst)) return PTR_ERR(dst); skb_dst_drop(skb); skb_dst_set(skb, dst); /* Change in oif may mean change in hh_len. */ hh_len = skb_dst(skb)->dev->hard_header_len; if (skb_headroom(skb) < hh_len && pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC)) return -ENOMEM; return 0; }

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jozsef kadlecsikjozsef kadlecsik2011.49%116.67%
eric w. biedermaneric w. biederman63.45%116.67%
dan carpenterdan carpenter63.45%116.67%
Total174100.00%6100.00%

EXPORT_SYMBOL(nf_xfrm_me_harder); #endif /* CONFIG_XFRM */
static u32 nf_nat_bysource_hash(const void *data, u32 len, u32 seed) { const struct nf_conntrack_tuple *t; const struct nf_conn *ct = data; t = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple; /* Original src, to ensure we map it consistently if poss. */ seed ^= net_hash_mix(nf_ct_net(ct)); return jhash2((const u32 *)&t->src, sizeof(t->src) / sizeof(u32), t->dst.protonum ^ seed); }

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florian westphalflorian westphal4955.68%233.33%
patrick mchardypatrick mchardy2730.68%116.67%
jozsef kadlecsikjozsef kadlecsik910.23%116.67%
daniel borkmanndaniel borkmann33.41%233.33%
Total88100.00%6100.00%

/* Is this tuple already taken? (not by us) */
int nf_nat_used_tuple(const struct nf_conntrack_tuple *tuple, const struct nf_conn *ignored_conntrack) { /* Conntrack tracking doesn't keep track of outgoing tuples; only * incoming ones. NAT means they don't have a fixed mapping, * so we invert the tuple and look for the incoming reply. * * We could keep a separate hash if this proves too slow. */ struct nf_conntrack_tuple reply; nf_ct_invert_tuplepr(&reply, tuple); return nf_conntrack_tuple_taken(&reply, ignored_conntrack); }

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EXPORT_SYMBOL(nf_nat_used_tuple); /* If we source map this tuple so reply looks like reply_tuple, will * that meet the constraints of range. */
static int in_range(const struct nf_nat_l3proto *l3proto, const struct nf_nat_l4proto *l4proto, const struct nf_conntrack_tuple *tuple, const struct nf_nat_range *range) { /* If we are supposed to map IPs, then we must be in the * range specified, otherwise let this drag us onto a new src IP. */ if (range->flags & NF_NAT_RANGE_MAP_IPS && !l3proto->in_range(tuple, range)) return 0; if (!(range->flags & NF_NAT_RANGE_PROTO_SPECIFIED) || l4proto->in_range(tuple, NF_NAT_MANIP_SRC, &range->min_proto, &range->max_proto)) return 1; return 0; }

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static inline int same_src(const struct nf_conn *ct, const struct nf_conntrack_tuple *tuple) { const struct nf_conntrack_tuple *t; t = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple; return (t->dst.protonum == tuple->dst.protonum && nf_inet_addr_cmp(&t->src.u3, &tuple->src.u3) && t->src.u.all == tuple->src.u.all); }

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patrick mchardypatrick mchardy4856.47%150.00%
jozsef kadlecsikjozsef kadlecsik3743.53%150.00%
Total85100.00%2100.00%


static int nf_nat_bysource_cmp(struct rhashtable_compare_arg *arg, const void *obj) { const struct nf_nat_conn_key *key = arg->key; const struct nf_conn *ct = obj; return same_src(ct, key->tuple) && net_eq(nf_ct_net(ct), key->net) && nf_ct_zone_equal(ct, key->zone, IP_CT_DIR_ORIGINAL); }

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florian westphalflorian westphal67100.00%1100.00%
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static struct rhashtable_params nf_nat_bysource_params = { .head_offset = offsetof(struct nf_conn, nat_bysource), .obj_hashfn = nf_nat_bysource_hash, .obj_cmpfn = nf_nat_bysource_cmp, .nelem_hint = 256, .min_size = 1024, .nulls_base = (1U << RHT_BASE_SHIFT), }; /* Only called for SRC manip */
static int find_appropriate_src(struct net *net, const struct nf_conntrack_zone *zone, const struct nf_nat_l3proto *l3proto, const struct nf_nat_l4proto *l4proto, const struct nf_conntrack_tuple *tuple, struct nf_conntrack_tuple *result, const struct nf_nat_range *range) { const struct nf_conn *ct; struct nf_nat_conn_key key = { .net = net, .tuple = tuple, .zone = zone }; ct = rhashtable_lookup_fast(&nf_nat_bysource_table, &key, nf_nat_bysource_params); if (!ct) return 0; nf_ct_invert_tuplepr(result, &ct->tuplehash[IP_CT_DIR_REPLY].tuple); result->dst = tuple->dst; return in_range(l3proto, l4proto, result, range); }

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jozsef kadlecsikjozsef kadlecsik5945.74%111.11%
florian westphalflorian westphal3728.68%222.22%
patrick mchardypatrick mchardy2015.50%222.22%
daniel borkmanndaniel borkmann75.43%222.22%
alexey dobriyanalexey dobriyan53.88%111.11%
jan engelhardtjan engelhardt10.78%111.11%
Total129100.00%9100.00%

/* For [FUTURE] fragmentation handling, we want the least-used * src-ip/dst-ip/proto triple. Fairness doesn't come into it. Thus * if the range specifies 1.2.3.4 ports 10000-10005 and 1.2.3.5 ports * 1-65535, we don't do pro-rata allocation based on ports; we choose * the ip with the lowest src-ip/dst-ip/proto usage. */
static void find_best_ips_proto(const struct nf_conntrack_zone *zone, struct nf_conntrack_tuple *tuple, const struct nf_nat_range *range, const struct nf_conn *ct, enum nf_nat_manip_type maniptype) { union nf_inet_addr *var_ipp; unsigned int i, max; /* Host order */ u32 minip, maxip, j, dist; bool full_range; /* No IP mapping? Do nothing. */ if (!(range->flags & NF_NAT_RANGE_MAP_IPS)) return; if (maniptype == NF_NAT_MANIP_SRC) var_ipp = &tuple->src.u3; else var_ipp = &tuple->dst.u3; /* Fast path: only one choice. */ if (nf_inet_addr_cmp(&range->min_addr, &range->max_addr)) { *var_ipp = range->min_addr; return; } if (nf_ct_l3num(ct) == NFPROTO_IPV4) max = sizeof(var_ipp->ip) / sizeof(u32) - 1; else max = sizeof(var_ipp->ip6) / sizeof(u32) - 1; /* Hashing source and destination IPs gives a fairly even * spread in practice (if there are a small number of IPs * involved, there usually aren't that many connections * anyway). The consistency means that servers see the same * client coming from the same IP (some Internet Banking sites * like this), even across reboots. */ j = jhash2((u32 *)&tuple->src.u3, sizeof(tuple->src.u3) / sizeof(u32), range->flags & NF_NAT_RANGE_PERSISTENT ? 0 : (__force u32)tuple->dst.u3.all[max] ^ zone->id); full_range = false; for (i = 0; i <= max; i++) { /* If first bytes of the address are at the maximum, use the * distance. Otherwise use the full range. */ if (!full_range) { minip = ntohl((__force __be32)range->min_addr.all[i]); maxip = ntohl((__force __be32)range->max_addr.all[i]); dist = maxip - minip + 1; } else { minip = 0; dist = ~0; } var_ipp->all[i] = (__force __u32) htonl(minip + reciprocal_scale(j, dist)); if (var_ipp->all[i] != range->max_addr.all[i]) full_range = true; if (!(range->flags & NF_NAT_RANGE_PERSISTENT)) j ^= (__force u32)tuple->dst.u3.all[i]; } }

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patrick mchardypatrick mchardy23161.27%550.00%
jozsef kadlecsikjozsef kadlecsik12934.22%110.00%
daniel borkmanndaniel borkmann102.65%220.00%
florian westphalflorian westphal51.33%110.00%
maximilian engelhardtmaximilian engelhardt20.53%110.00%
Total377100.00%10100.00%

/* Manipulate the tuple into the range given. For NF_INET_POST_ROUTING, * we change the source to map into the range. For NF_INET_PRE_ROUTING * and NF_INET_LOCAL_OUT, we change the destination to map into the * range. It might not be possible to get a unique tuple, but we try. * At worst (or if we race), we will end up with a final duplicate in * __ip_conntrack_confirm and drop the packet. */
static void get_unique_tuple(struct nf_conntrack_tuple *tuple, const struct nf_conntrack_tuple *orig_tuple, const struct nf_nat_range *range, struct nf_conn *ct, enum nf_nat_manip_type maniptype) { const struct nf_conntrack_zone *zone; const struct nf_nat_l3proto *l3proto; const struct nf_nat_l4proto *l4proto; struct net *net = nf_ct_net(ct); zone = nf_ct_zone(ct); rcu_read_lock(); l3proto = __nf_nat_l3proto_find(orig_tuple->src.l3num); l4proto = __nf_nat_l4proto_find(orig_tuple->src.l3num, orig_tuple->dst.protonum); /* 1) If this srcip/proto/src-proto-part is currently mapped, * and that same mapping gives a unique tuple within the given * range, use that. * * This is only required for source (ie. NAT/masq) mappings. * So far, we don't do local source mappings, so multiple * manips not an issue. */ if (maniptype == NF_NAT_MANIP_SRC && !(range->flags & NF_NAT_RANGE_PROTO_RANDOM_ALL)) { /* try the original tuple first */ if (in_range(l3proto, l4proto, orig_tuple, range)) { if (!nf_nat_used_tuple(orig_tuple, ct)) { *tuple = *orig_tuple; goto out; } } else if (find_appropriate_src(net, zone, l3proto, l4proto, orig_tuple, tuple, range)) { pr_debug("get_unique_tuple: Found current src map\n"); if (!nf_nat_used_tuple(tuple, ct)) goto out; } } /* 2) Select the least-used IP/proto combination in the given range */ *tuple = *orig_tuple; find_best_ips_proto(zone, tuple, range, ct, maniptype); /* 3) The per-protocol part of the manip is made to map into * the range to make a unique tuple. */ /* Only bother mapping if it's not already in range and unique */ if (!(range->flags & NF_NAT_RANGE_PROTO_RANDOM_ALL)) { if (range->flags & NF_NAT_RANGE_PROTO_SPECIFIED) { if (l4proto->in_range(tuple, maniptype, &range->min_proto, &range->max_proto) && (range->min_proto.all == range->max_proto.all || !nf_nat_used_tuple(tuple, ct))) goto out; } else if (!nf_nat_used_tuple(tuple, ct)) { goto out; } } /* Last change: get protocol to try to obtain unique tuple. */ l4proto->unique_tuple(l3proto, tuple, range, maniptype, ct); out: rcu_read_unlock(); }

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jozsef kadlecsikjozsef kadlecsik13241.12%17.14%
patrick mchardypatrick mchardy9128.35%535.71%
changli gaochangli gao7021.81%428.57%
alexey dobriyanalexey dobriyan123.74%17.14%
daniel borkmanndaniel borkmann103.12%214.29%
eric leblonderic leblond61.87%17.14%
Total321100.00%14100.00%


struct nf_conn_nat *nf_ct_nat_ext_add(struct nf_conn *ct) { struct nf_conn_nat *nat = nfct_nat(ct); if (nat) return nat; if (!nf_ct_is_confirmed(ct)) nat = nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC); return nat; }

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EXPORT_SYMBOL_GPL(nf_ct_nat_ext_add);
unsigned int nf_nat_setup_info(struct nf_conn *ct, const struct nf_nat_range *range, enum nf_nat_manip_type maniptype) { struct nf_conntrack_tuple curr_tuple, new_tuple; struct nf_conn_nat *nat; /* nat helper or nfctnetlink also setup binding */ nat = nf_ct_nat_ext_add(ct); if (nat == NULL) return NF_ACCEPT; NF_CT_ASSERT(maniptype == NF_NAT_MANIP_SRC || maniptype == NF_NAT_MANIP_DST); BUG_ON(nf_nat_initialized(ct, maniptype)); /* What we've got will look like inverse of reply. Normally * this is what is in the conntrack, except for prior * manipulations (future optimization: if num_manips == 0, * orig_tp = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple) */ nf_ct_invert_tuplepr(&curr_tuple, &ct->tuplehash[IP_CT_DIR_REPLY].tuple); get_unique_tuple(&new_tuple, &curr_tuple, range, ct, maniptype); if (!nf_ct_tuple_equal(&new_tuple, &curr_tuple)) { struct nf_conntrack_tuple reply; /* Alter conntrack table so will recognize replies. */ nf_ct_invert_tuplepr(&reply, &new_tuple); nf_conntrack_alter_reply(ct, &reply); /* Non-atomic: we own this at the moment. */ if (maniptype == NF_NAT_MANIP_SRC) ct->status |= IPS_SRC_NAT; else ct->status |= IPS_DST_NAT; if (nfct_help(ct)) if (!nfct_seqadj_ext_add(ct)) return NF_DROP; } if (maniptype == NF_NAT_MANIP_SRC) { int err; err = rhashtable_insert_fast(&nf_nat_bysource_table, &ct->nat_bysource, nf_nat_bysource_params); if (err) return NF_DROP; } /* It's done. */ if (maniptype == NF_NAT_MANIP_DST) ct->status |= IPS_DST_NAT_DONE; else ct->status |= IPS_SRC_NAT_DONE; return NF_ACCEPT; }

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jozsef kadlecsikjozsef kadlecsik16470.69%17.69%
patrick mchardypatrick mchardy239.91%430.77%
florian westphalflorian westphal166.90%323.08%
yasuyuki kozakaiyasuyuki kozakai166.90%17.69%
gao fenggao feng73.02%17.69%
changli gaochangli gao62.59%323.08%
Total232100.00%13100.00%

EXPORT_SYMBOL(nf_nat_setup_info);
static unsigned int __nf_nat_alloc_null_binding(struct nf_conn *ct, enum nf_nat_manip_type manip) { /* Force range to this IP; let proto decide mapping for * per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED). * Use reply in case it's already been mangled (eg local packet). */ union nf_inet_addr ip = (manip == NF_NAT_MANIP_SRC ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3 : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3); struct nf_nat_range range = { .flags = NF_NAT_RANGE_MAP_IPS, .min_addr = ip, .max_addr = ip, }; return nf_nat_setup_info(ct, &range, manip); }

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unsigned int nf_nat_alloc_null_binding(struct nf_conn *ct, unsigned int hooknum) { return __nf_nat_alloc_null_binding(ct, HOOK2MANIP(hooknum)); }

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EXPORT_SYMBOL_GPL(nf_nat_alloc_null_binding); /* Do packet manipulations according to nf_nat_setup_info. */
unsigned int nf_nat_packet(struct nf_conn *ct, enum ip_conntrack_info ctinfo, unsigned int hooknum, struct sk_buff *skb) { const struct nf_nat_l3proto *l3proto; const struct nf_nat_l4proto *l4proto; enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); unsigned long statusbit; enum nf_nat_manip_type mtype = HOOK2MANIP(hooknum); if (mtype == NF_NAT_MANIP_SRC) statusbit = IPS_SRC_NAT; else statusbit = IPS_DST_NAT; /* Invert if this is reply dir. */ if (dir == IP_CT_DIR_REPLY) statusbit ^= IPS_NAT_MASK; /* Non-atomic: these bits don't change. */ if (ct->status & statusbit) { struct nf_conntrack_tuple target; /* We are aiming to look like inverse of other direction. */ nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple); l3proto = __nf_nat_l3proto_find(target.src.l3num); l4proto = __nf_nat_l4proto_find(target.src.l3num, target.dst.protonum); if (!l3proto->manip_pkt(skb, 0, l4proto, &target, mtype)) return NF_DROP; } return NF_ACCEPT; }

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patrick mchardypatrick mchardy4425.88%250.00%
herbert xuherbert xu21.18%125.00%
Total170100.00%4100.00%

EXPORT_SYMBOL_GPL(nf_nat_packet); struct nf_nat_proto_clean { u8 l3proto; u8 l4proto; }; /* kill conntracks with affected NAT section */
static int nf_nat_proto_remove(struct nf_conn *i, void *data) { const struct nf_nat_proto_clean *clean = data; struct nf_conn_nat *nat = nfct_nat(i); if (!nat) return 0; if ((clean->l3proto && nf_ct_l3num(i) != clean->l3proto) || (clean->l4proto && nf_ct_protonum(i) != clean->l4proto)) return 0; return i->status & IPS_NAT_MASK ? 1 : 0; }

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patrick mchardypatrick mchardy4248.28%133.33%
jozsef kadlecsikjozsef kadlecsik3944.83%133.33%
florian westphalflorian westphal66.90%133.33%
Total87100.00%3100.00%


static int nf_nat_proto_clean(struct nf_conn *ct, void *data) { struct nf_conn_nat *nat = nfct_nat(ct); if (nf_nat_proto_remove(ct, data)) return 1; if (!nat) return 0; /* This netns is being destroyed, and conntrack has nat null binding. * Remove it from bysource hash, as the table will be freed soon. * * Else, when the conntrack is destoyed, nf_nat_cleanup_conntrack() * will delete entry from already-freed table. */ if (!del_timer(&ct->timeout)) return 1; ct->status &= ~IPS_NAT_DONE_MASK; rhashtable_remove_fast(&nf_nat_bysource_table, &ct->nat_bysource, nf_nat_bysource_params); add_timer(&ct->timeout); /* don't delete conntrack. Although that would make things a lot * simpler, we'd end up flushing all conntracks on nat rmmod. */ return 0; }

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static void nf_nat_l4proto_clean(u8 l3proto, u8 l4proto) { struct nf_nat_proto_clean clean = { .l3proto = l3proto, .l4proto = l4proto, }; struct net *net; rtnl_lock(); for_each_net(net) nf_ct_iterate_cleanup(net, nf_nat_proto_remove, &clean, 0, 0); rtnl_unlock(); }

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patrick mchardypatrick mchardy4782.46%120.00%
florian westphalflorian westphal58.77%240.00%
julian anastasovjulian anastasov35.26%120.00%
jozsef kadlecsikjozsef kadlecsik23.51%120.00%
Total57100.00%5100.00%


static void nf_nat_l3proto_clean(u8 l3proto) { struct nf_nat_proto_clean clean = { .l3proto = l3proto, }; struct net *net; rtnl_lock(); for_each_net(net) nf_ct_iterate_cleanup(net, nf_nat_proto_remove, &clean, 0, 0); rtnl_unlock(); }

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patrick mchardypatrick mchardy4183.67%125.00%
florian westphalflorian westphal510.20%250.00%
jozsef kadlecsikjozsef kadlecsik36.12%125.00%
Total49100.00%4100.00%

/* Protocol registration. */
int nf_nat_l4proto_register(u8 l3proto, const struct nf_nat_l4proto *l4proto) { const struct nf_nat_l4proto **l4protos; unsigned int i; int ret = 0; mutex_lock(&nf_nat_proto_mutex); if (nf_nat_l4protos[l3proto] == NULL) { l4protos = kmalloc(IPPROTO_MAX * sizeof(struct nf_nat_l4proto *), GFP_KERNEL); if (l4protos == NULL) { ret = -ENOMEM; goto out; } for (i = 0; i < IPPROTO_MAX; i++) RCU_INIT_POINTER(l4protos[i], &nf_nat_l4proto_unknown); /* Before making proto_array visible to lockless readers, * we must make sure its content is committed to memory. */ smp_wmb(); nf_nat_l4protos[l3proto] = l4protos; } if (rcu_dereference_protected( nf_nat_l4protos[l3proto][l4proto->l4proto], lockdep_is_held(&nf_nat_proto_mutex) ) != &nf_nat_l4proto_unknown) { ret = -EBUSY; goto out; } RCU_INIT_POINTER(nf_nat_l4protos[l3proto][l4proto->l4proto], l4proto); out: mutex_unlock(&nf_nat_proto_mutex); return ret; }

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PersonTokensPropCommitsCommitProp
patrick mchardypatrick mchardy15488.51%150.00%
jozsef kadlecsikjozsef kadlecsik2011.49%150.00%
Total174100.00%2100.00%

EXPORT_SYMBOL_GPL(nf_nat_l4proto_register); /* No one stores the protocol anywhere; simply delete it. */
void nf_nat_l4proto_unregister(u8 l3proto, const struct nf_nat_l4proto *l4proto) { mutex_lock(&nf_nat_proto_mutex); RCU_INIT_POINTER(nf_nat_l4protos[l3proto][l4proto->l4proto], &nf_nat_l4proto_unknown); mutex_unlock(&nf_nat_proto_mutex); synchronize_rcu(); nf_nat_l4proto_clean(l3proto, l4proto->l4proto);