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    Subject[PATCH v7 bpf-next 01/11] net: Introduce net.ipv4.tcp_migrate_req.
    Date
    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>
    Reviewed-by: Benjamin Herrenschmidt <benh@amazon.com>
    Acked-by: Martin KaFai Lau <kafai@fb.com>
    ---
    Documentation/networking/ip-sysctl.rst | 25 +++++++++++++++++++++++++
    include/net/netns/ipv4.h | 1 +
    net/ipv4/sysctl_net_ipv4.c | 9 +++++++++
    3 files changed, 35 insertions(+)

    diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
    index a5c250044500..b0436d3a4f11 100644
    --- a/Documentation/networking/ip-sysctl.rst
    +++ b/Documentation/networking/ip-sysctl.rst
    @@ -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.
    diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
    index 746c80cd4257..b8620519eace 100644
    --- a/include/net/netns/ipv4.h
    +++ b/include/net/netns/ipv4.h
    @@ -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;
    diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
    index 4fa77f182dcb..6f1e64d49232 100644
    --- a/net/ipv4/sysctl_net_ipv4.c
    +++ b/net/ipv4/sysctl_net_ipv4.c
    @@ -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,
    --
    2.30.2
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