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Commit 6ed5943f authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso
Browse files

netfilter: nat: remove l4 protocol port rovers 



This is a leftover from days where single-cpu systems were common:
Store last port used to resolve a clash to use it as a starting point when
the next conflict needs to be resolved.

When we have parallel attempt to connect to same address:port pair,
its likely that both cores end up computing the same "available" port,
as both use same starting port, and newly used ports won't become
visible to other cores until the conntrack gets confirmed later.

One of the cores then has to drop the packet at insertion time because
the chosen new tuple turns out to be in use after all.

Lets simplify this: remove port rover and use a pseudo-random starting
point.

Note that this doesn't make netfilter default to 'fully random' mode;
the 'rover' was only used if NAT could not reuse source port as-is.

Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent c3e93059

include/net/netfilter/nf_nat_l4proto.h

+1 −1
Original line number Diff line number Diff line
@@ -74,7 +74,7 @@ void nf_nat_l4proto_unique_tuple(const struct nf_nat_l3proto *l3proto, 
				 struct nf_conntrack_tuple *tuple,

				 const struct nf_nat_range2 *range,

				 enum nf_nat_manip_type maniptype,

				 const struct nf_conn *ct, u16 *rover);

				 const struct nf_conn *ct);



int nf_nat_l4proto_nlattr_to_range(struct nlattr *tb[],

				   struct nf_nat_range2 *range);

net/netfilter/nf_nat_proto_common.c

+2 −6
Original line number Diff line number Diff line
@@ -38,8 +38,7 @@ void nf_nat_l4proto_unique_tuple(const struct nf_nat_l3proto *l3proto, 
				 struct nf_conntrack_tuple *tuple,

				 const struct nf_nat_range2 *range,

				 enum nf_nat_manip_type maniptype,

				 const struct nf_conn *ct,

				 u16 *rover)

				 const struct nf_conn *ct)

{

	unsigned int range_size, min, max, i;

	__be16 *portptr;
@@ -86,16 +85,13 @@ void nf_nat_l4proto_unique_tuple(const struct nf_nat_l3proto *l3proto, 
	} else if (range->flags & NF_NAT_RANGE_PROTO_OFFSET) {

		off = (ntohs(*portptr) - ntohs(range->base_proto.all));

	} else {

		off = *rover;

		off = prandom_u32();

	}



	for (i = 0; ; ++off) {

		*portptr = htons(min + off % range_size);

		if (++i != range_size && nf_nat_used_tuple(tuple, ct))

			continue;

		if (!(range->flags & (NF_NAT_RANGE_PROTO_RANDOM_ALL|

					NF_NAT_RANGE_PROTO_OFFSET)))

			*rover = off;

		return;

	}

}

net/netfilter/nf_nat_proto_dccp.c

+1 −4
Original line number Diff line number Diff line
@@ -18,8 +18,6 @@ 
#include <net/netfilter/nf_nat_l3proto.h>

#include <net/netfilter/nf_nat_l4proto.h>



static u_int16_t dccp_port_rover;



static void

dccp_unique_tuple(const struct nf_nat_l3proto *l3proto,

		  struct nf_conntrack_tuple *tuple,
@@ -27,8 +25,7 @@ dccp_unique_tuple(const struct nf_nat_l3proto *l3proto, 
		  enum nf_nat_manip_type maniptype,

		  const struct nf_conn *ct)

{

	nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct,

				    &dccp_port_rover);

	nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct);

}



static bool

net/netfilter/nf_nat_proto_sctp.c

+1 −4
Original line number Diff line number Diff line
@@ -12,8 +12,6 @@ 


#include <net/netfilter/nf_nat_l4proto.h>



static u_int16_t nf_sctp_port_rover;



static void

sctp_unique_tuple(const struct nf_nat_l3proto *l3proto,

		  struct nf_conntrack_tuple *tuple,
@@ -21,8 +19,7 @@ sctp_unique_tuple(const struct nf_nat_l3proto *l3proto, 
		  enum nf_nat_manip_type maniptype,

		  const struct nf_conn *ct)

{

	nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct,

				    &nf_sctp_port_rover);

	nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct);

}



static bool

net/netfilter/nf_nat_proto_tcp.c

+1 −4
Original line number Diff line number Diff line
@@ -18,8 +18,6 @@ 
#include <net/netfilter/nf_nat_l4proto.h>

#include <net/netfilter/nf_nat_core.h>



static u16 tcp_port_rover;



static void

tcp_unique_tuple(const struct nf_nat_l3proto *l3proto,

		 struct nf_conntrack_tuple *tuple,
@@ -27,8 +25,7 @@ tcp_unique_tuple(const struct nf_nat_l3proto *l3proto, 
		 enum nf_nat_manip_type maniptype,

		 const struct nf_conn *ct)

{

	nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct,

				    &tcp_port_rover);

	nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct);

}



static bool