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Commit 86136bf6 authored by Gleb Mazovetskiy's avatar Gleb Mazovetskiy Committed by Greg Kroah-Hartman
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tcp: configurable source port perturb table size 



[ Upstream commit aeac4ec8f46d610a10adbaeff5e2edf6a88ffc62 ]

On embedded systems with little memory and no relevant
security concerns, it is beneficial to reduce the size
of the table.

Reducing the size from 2^16 to 2^8 saves 255 KiB
of kernel RAM.

Makes the table size configurable as an expert option.

The size was previously increased from 2^8 to 2^16
in commit 4c2c8f03a5ab ("tcp: increase source port perturb table to
2^16").

Signed-off-by: default avatarGleb Mazovetskiy <glex.spb@gmail.com>
Reviewed-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 07da8fca

net/ipv4/Kconfig

+10 −0
Original line number Diff line number Diff line
@@ -389,6 +389,16 @@ config INET_IPCOMP 


	  If unsure, say Y.



config INET_TABLE_PERTURB_ORDER

	int "INET: Source port perturbation table size (as power of 2)" if EXPERT

	default 16

	help

	  Source port perturbation table size (as power of 2) for

	  RFC 6056 3.3.4.  Algorithm 4: Double-Hash Port Selection Algorithm.



	  The default is almost always what you want.

	  Only change this if you know what you are doing.



config INET_XFRM_TUNNEL

	tristate

	select INET_TUNNEL

net/ipv4/inet_hashtables.c

+5 −5
Original line number Diff line number Diff line
@@ -675,13 +675,13 @@ EXPORT_SYMBOL_GPL(inet_unhash); 
 * Note that we use 32bit integers (vs RFC 'short integers')

 * because 2^16 is not a multiple of num_ephemeral and this

 * property might be used by clever attacker.

 *

 * RFC claims using TABLE_LENGTH=10 buckets gives an improvement, though

 * attacks were since demonstrated, thus we use 65536 instead to really

 * give more isolation and privacy, at the expense of 256kB of kernel

 * memory.

 * attacks were since demonstrated, thus we use 65536 by default instead

 * to really give more isolation and privacy, at the expense of 256kB

 * of kernel memory.

 */

#define INET_TABLE_PERTURB_SHIFT 16

#define INET_TABLE_PERTURB_SIZE (1 << INET_TABLE_PERTURB_SHIFT)

#define INET_TABLE_PERTURB_SIZE (1 << CONFIG_INET_TABLE_PERTURB_ORDER)

static u32 *table_perturb;



int __inet_hash_connect(struct inet_timewait_death_row *death_row,