From: Gleb Mazovetskiy glex.spb@gmail.com
[ 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: Gleb Mazovetskiy glex.spb@gmail.com Reviewed-by: Kuniyuki Iwashima kuniyu@amazon.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv4/Kconfig | 10 ++++++++++ net/ipv4/inet_hashtables.c | 10 +++++----- 2 files changed, 15 insertions(+), 5 deletions(-)
diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig index 87983e70f03f..23b06063e1a5 100644 --- a/net/ipv4/Kconfig +++ b/net/ipv4/Kconfig @@ -403,6 +403,16 @@ 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 diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c index ce6a3873f89e..0d378da4b1b1 100644 --- a/net/ipv4/inet_hashtables.c +++ b/net/ipv4/inet_hashtables.c @@ -721,13 +721,13 @@ 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,