Messages in this thread Patch in this message | | | From | Kuniyuki Iwashima <> | Subject | Re: [PATCH 1/1] tcp: configurable source port perturb table size | Date | Tue, 15 Nov 2022 17:32:08 -0800 |
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From: Gleb Mazovetskiy <glex.spb@gmail.com> Date: Mon, 14 Nov 2022 22:56:16 +0000 > 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>
Looks good.
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> --- > 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 e983bb0c5012..2dfb12230f08 100644 > --- a/net/ipv4/Kconfig > +++ b/net/ipv4/Kconfig > @@ -402,6 +402,16 @@ 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 d3dc28156622..033bf3c2538f 100644 > --- a/net/ipv4/inet_hashtables.c > +++ b/net/ipv4/inet_hashtables.c > @@ -906,13 +906,13 @@ EXPORT_SYMBOL_GPL(inet_bhash2_update_saddr); > * 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, > -- > 2.37.2
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