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netfilter: add SYNPROXY core/target

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Add a SYNPROXY for netfilter. The code is split into two parts, the synproxy
core with common functions and an address family specific target.

The SYNPROXY receives the connection request from the client, responds with
a SYN/ACK containing a SYN cookie and announcing a zero window and checks
whether the final ACK from the client contains a valid cookie.

It then establishes a connection to the original destination and, if
successful, sends a window update to the client with the window size
announced by the server.

Support for timestamps, SACK, window scaling and MSS options can be
statically configured as target parameters if the features of the server
are known. If timestamps are used, the timestamp value sent back to
the client in the SYN/ACK will be different from the real timestamp of
the server. In order to now break PAWS, the timestamps are translated in
the direction server->client.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Tested-by: Martin Topholm <mph@one.com>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Patrick McHardy
2013-08-27 08:50:14 +02:00
committed by Pablo Neira Ayuso
parent 0198230b77
commit 48b1de4c11
13 changed files with 1066 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
include/net/netfilter/nf_conntrack_extend.h
View File

@@ -9,8 +9,8 @@ enum nf_ct_ext_id {
NF_CT_EXT_HELPER,
#if defined(CONFIG_NF_NAT) || defined(CONFIG_NF_NAT_MODULE)
NF_CT_EXT_NAT,
NF_CT_EXT_SEQADJ,
#endif
NF_CT_EXT_SEQADJ,
NF_CT_EXT_ACCT,
#ifdef CONFIG_NF_CONNTRACK_EVENTS
NF_CT_EXT_ECACHE,
@@ -26,6 +26,9 @@ enum nf_ct_ext_id {
#endif
#ifdef CONFIG_NF_CONNTRACK_LABELS
NF_CT_EXT_LABELS,
#endif
#if IS_ENABLED(CONFIG_NETFILTER_SYNPROXY)
NF_CT_EXT_SYNPROXY,
#endif
NF_CT_EXT_NUM,
};
@@ -39,6 +42,7 @@ enum nf_ct_ext_id {
#define NF_CT_EXT_TSTAMP_TYPE struct nf_conn_tstamp
#define NF_CT_EXT_TIMEOUT_TYPE struct nf_conn_timeout
#define NF_CT_EXT_LABELS_TYPE struct nf_conn_labels
#define NF_CT_EXT_SYNPROXY_TYPE struct nf_conn_synproxy
/* Extensions: optional stuff which isn't permanently in struct. */
struct nf_ct_ext {

2
include/net/netfilter/nf_conntrack_seqadj.h
View File

@@ -30,6 +30,8 @@ static inline struct nf_conn_seqadj *nfct_seqadj_ext_add(struct nf_conn *ct)
return nf_ct_ext_add(ct, NF_CT_EXT_SEQADJ, GFP_ATOMIC);
}
extern int nf_ct_seqadj_init(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
s32 off);
extern int nf_ct_seqadj_set(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
__be32 seq, s32 off);
extern void nf_ct_tcp_seqadj_set(struct sk_buff *skb,

77
include/net/netfilter/nf_conntrack_synproxy.h Normal file
View File

@@ -0,0 +1,77 @@
#ifndef _NF_CONNTRACK_SYNPROXY_H
#define _NF_CONNTRACK_SYNPROXY_H
#include <net/netns/generic.h>
struct nf_conn_synproxy {
u32 isn;
u32 its;
u32 tsoff;
};
static inline struct nf_conn_synproxy *nfct_synproxy(const struct nf_conn *ct)
{
#if IS_ENABLED(CONFIG_NETFILTER_SYNPROXY)
return nf_ct_ext_find(ct, NF_CT_EXT_SYNPROXY);
#else
return NULL;
#endif
}
static inline struct nf_conn_synproxy *nfct_synproxy_ext_add(struct nf_conn *ct)
{
#if IS_ENABLED(CONFIG_NETFILTER_SYNPROXY)
return nf_ct_ext_add(ct, NF_CT_EXT_SYNPROXY, GFP_ATOMIC);
#else
return NULL;
#endif
}
struct synproxy_stats {
unsigned int syn_received;
unsigned int cookie_invalid;
unsigned int cookie_valid;
unsigned int cookie_retrans;
unsigned int conn_reopened;
};
struct synproxy_net {
struct nf_conn *tmpl;
struct synproxy_stats __percpu *stats;
};
extern int synproxy_net_id;
static inline struct synproxy_net *synproxy_pernet(struct net *net)
{
return net_generic(net, synproxy_net_id);
}
struct synproxy_options {
u8 options;
u8 wscale;
u16 mss;
u32 tsval;
u32 tsecr;
};
struct tcphdr;
struct xt_synproxy_info;
extern void synproxy_parse_options(const struct sk_buff *skb, unsigned int doff,
const struct tcphdr *th,
struct synproxy_options *opts);
extern unsigned int synproxy_options_size(const struct synproxy_options *opts);
extern void synproxy_build_options(struct tcphdr *th,
const struct synproxy_options *opts);
extern void synproxy_init_timestamp_cookie(const struct xt_synproxy_info *info,
struct synproxy_options *opts);
extern void synproxy_check_timestamp_cookie(struct synproxy_options *opts);
extern unsigned int synproxy_tstamp_adjust(struct sk_buff *skb,
unsigned int protoff,
struct tcphdr *th,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo,
const struct nf_conn_synproxy *synproxy);
#endif /* _NF_CONNTRACK_SYNPROXY_H */