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net: Introduce net.ipv4.tcp_migrate_req. 

This commit adds a new sysctl option: net.ipv4.tcp_migrate_req. If this
option is enabled or eBPF program is attached, we will be able to migrate
child sockets from a listener to another in the same reuseport group after
close() or shutdown() syscalls.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Benjamin Herrenschmidt <benh@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20210612123224.12525-2-kuniyu@amazon.co.jp
This commit is contained in:
Kuniyuki Iwashima 2021-06-12 21:32:14 +09:00 committed by Daniel Borkmann
parent bbf29d3a2e
commit f9ac779f88
3 changed files with 35 additions and 0 deletions
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25
Documentation/networking/ip-sysctl.rst
View File

@ -761,6 +761,31 @@ tcp_syncookies - INTEGER
network connections you can set this knob to 2 to enable
unconditionally generation of syncookies.
tcp_migrate_req - BOOLEAN
The incoming connection is tied to a specific listening socket when
the initial SYN packet is received during the three-way handshake.
When a listener is closed, in-flight request sockets during the
handshake and established sockets in the accept queue are aborted.
If the listener has SO_REUSEPORT enabled, other listeners on the
same port should have been able to accept such connections. This
option makes it possible to migrate such child sockets to another
listener after close() or shutdown().
The BPF_SK_REUSEPORT_SELECT_OR_MIGRATE type of eBPF program should
usually be used to define the policy to pick an alive listener.
Otherwise, the kernel will randomly pick an alive listener only if
this option is enabled.
Note that migration between listeners with different settings may
crash applications. Let's say migration happens from listener A to
B, and only B has TCP_SAVE_SYN enabled. B cannot read SYN data from
the requests migrated from A. To avoid such a situation, cancel
migration by returning SK_DROP in the type of eBPF program, or
disable this option.
Default: 0
tcp_fastopen - INTEGER
Enable TCP Fast Open (RFC7413) to send and accept data in the opening
SYN packet.

1
include/net/netns/ipv4.h
View File

@ -126,6 +126,7 @@ struct netns_ipv4 {
u8 sysctl_tcp_syn_retries;
u8 sysctl_tcp_synack_retries;
u8 sysctl_tcp_syncookies;
u8 sysctl_tcp_migrate_req;
int sysctl_tcp_reordering;
u8 sysctl_tcp_retries1;
u8 sysctl_tcp_retries2;

9
net/ipv4/sysctl_net_ipv4.c
View File

@ -960,6 +960,15 @@ static struct ctl_table ipv4_net_table[] = {
.proc_handler = proc_dou8vec_minmax,
},
#endif
{
.procname = "tcp_migrate_req",
.data = &init_net.ipv4.sysctl_tcp_migrate_req,
.maxlen = sizeof(u8),
.mode = 0644,
.proc_handler = proc_dou8vec_minmax,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE
},
{
.procname = "tcp_reordering",
.data = &init_net.ipv4.sysctl_tcp_reordering,