netdev - [PATCH net-next 1/3] net: increase optmem

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20231214104901.1318423-2-edumazet@google.com>
Date: Thu, 14 Dec 2023 10:48:59 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Neal Cardwell <ncardwell@...gle.com>, Willem de Bruijn <willemb@...gle.com>, 
	Mina Almasry <almasrymina@...gle.com>, Chao Wu <wwchao@...gle.com>, 
	Pavel Begunkov <asml.silence@...il.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 1/3] net: increase optmem_max default value

For many years, /proc/sys/net/core/optmem_max default value
on a 64bit kernel has been 20 KB.

Regular usage of TCP tx zerocopy needs a bit more.

Google has used 128KB as the default value for 7 years without
any problem.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 Documentation/admin-guide/sysctl/net.rst | 5 ++++-
 net/core/sock.c                          | 6 ++++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/sysctl/net.rst b/Documentation/admin-guide/sysctl/net.rst
index c7525942f12ce996e55afd3f2badda30ffe3c311..3960916519557f60cb91a7477015a5aca285e268 100644
--- a/Documentation/admin-guide/sysctl/net.rst
+++ b/Documentation/admin-guide/sysctl/net.rst
@@ -345,7 +345,10 @@ optmem_max
 ----------
 
 Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence
-of struct cmsghdr structures with appended data.
+of struct cmsghdr structures with appended data. TCP tx zerocopy also uses
+optmem_max as a limit for its internal structures.
+
+Default : 128 KB
 
 fb_tunnels_only_for_init_net
 ----------------------------
diff --git a/net/core/sock.c b/net/core/sock.c
index fef349dd72fa735b5915fc03e29cbb155b2aff2c..08ecdc68d2df6167f0d45f7e421e307cdc2f0038 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -283,8 +283,10 @@ EXPORT_SYMBOL(sysctl_rmem_max);
 __u32 sysctl_wmem_default __read_mostly = SK_WMEM_MAX;
 __u32 sysctl_rmem_default __read_mostly = SK_RMEM_MAX;
 
-/* Maximal space eaten by iovec or ancillary data plus some space */
-int sysctl_optmem_max __read_mostly = sizeof(unsigned long)*(2*UIO_MAXIOV+512);
+/* Limits per socket sk_omem_alloc usage.
+ * TCP zerocopy regular usage needs 128 KB.
+ */
+int sysctl_optmem_max __read_mostly = 128 * 1024;
 EXPORT_SYMBOL(sysctl_optmem_max);
 
 int sysctl_tstamp_allow_data __read_mostly = 1;
-- 
2.43.0.472.g3155946c3a-goog