Re: [PATCH net-next v5 07/14] ipv4, ipv6: Use splice_eof() to flush

From: Kuniyuki Iwashima
Date: Wed Jun 07 2023 - 11:33:09 EST

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From: David Howells <dhowells@xxxxxxxxxx>
Date: Wed, 7 Jun 2023 15:05:52 +0100
> Allow splice to undo the effects of MSG_MORE after prematurely ending a
> splice/sendfile due to getting an EOF condition (->splice_read() returned
> 0) after splice had called sendmsg() with MSG_MORE set when the user didn't
> set MSG_MORE.
>
> For UDP, a pending packet will not be emitted if the socket is closed
> before it is flushed; with this change, it be flushed by ->splice_eof().
>
> For TCP, it's not clear that MSG_MORE is actually effective.
>
> Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Link: https://lore.kernel.org/r/CAHk-=wh=V579PDYvkpnTobCLGczbgxpMgGmmhqiTyE34Cpi5Gg@xxxxxxxxxxxxxx/
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> cc: Willem de Bruijn <willemdebruijn.kernel@xxxxxxxxx>
> cc: David Ahern <dsahern@xxxxxxxxxx>
> cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> cc: Jens Axboe <axboe@xxxxxxxxx>
> cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> cc: netdev@xxxxxxxxxxxxxxx
> ---
> include/net/inet_common.h | 1 +
> include/net/tcp.h | 1 +
> include/net/udp.h | 1 +
> net/ipv4/af_inet.c | 18 ++++++++++++++++++
> net/ipv4/tcp.c | 16 ++++++++++++++++
> net/ipv4/tcp_ipv4.c | 1 +
> net/ipv4/udp.c | 16 ++++++++++++++++
> net/ipv6/af_inet6.c | 1 +
> net/ipv6/tcp_ipv6.c | 1 +
> net/ipv6/udp.c | 18 ++++++++++++++++++
> 10 files changed, 74 insertions(+)
>
> diff --git a/include/net/inet_common.h b/include/net/inet_common.h
> index 77f4b0ef5b92..a75333342c4e 100644
> --- a/include/net/inet_common.h
> +++ b/include/net/inet_common.h
> @@ -35,6 +35,7 @@ void __inet_accept(struct socket *sock, struct socket *newsock,
> struct sock *newsk);
> int inet_send_prepare(struct sock *sk);
> int inet_sendmsg(struct socket *sock, struct msghdr *msg, size_t size);
> +void inet_splice_eof(struct socket *sock);
> ssize_t inet_sendpage(struct socket *sock, struct page *page, int offset,
> size_t size, int flags);
> int inet_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 68990a8f556a..49611af31bb7 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -327,6 +327,7 @@ int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
> int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size);
> int tcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg, int *copied,
> size_t size, struct ubuf_info *uarg);
> +void tcp_splice_eof(struct socket *sock);
> int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
> int flags);
> int tcp_sendpage_locked(struct sock *sk, struct page *page, int offset,
> diff --git a/include/net/udp.h b/include/net/udp.h
> index 5cad44318d71..4ed0b47c5582 100644
> --- a/include/net/udp.h
> +++ b/include/net/udp.h
> @@ -278,6 +278,7 @@ int udp_get_port(struct sock *sk, unsigned short snum,
> int udp_err(struct sk_buff *, u32);
> int udp_abort(struct sock *sk, int err);
> int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len);
> +void udp_splice_eof(struct socket *sock);
> int udp_push_pending_frames(struct sock *sk);
> void udp_flush_pending_frames(struct sock *sk);
> int udp_cmsg_send(struct sock *sk, struct msghdr *msg, u16 *gso_size);
> diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
> index b5735b3551cf..6cfb78592836 100644
> --- a/net/ipv4/af_inet.c
> +++ b/net/ipv4/af_inet.c
> @@ -831,6 +831,21 @@ int inet_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
> }
> EXPORT_SYMBOL(inet_sendmsg);
>
> +void inet_splice_eof(struct socket *sock)
> +{
> + const struct proto *prot;
> + struct sock *sk = sock->sk;
> +
> + if (unlikely(inet_send_prepare(sk)))
> + return;
> +
> + /* IPV6_ADDRFORM can change sk->sk_prot under us. */
> + prot = READ_ONCE(sk->sk_prot);
> + if (prot->splice_eof)
> + sk->sk_prot->splice_eof(sock);

We need to use prot here.

> +}
> +EXPORT_SYMBOL_GPL(inet_splice_eof);
> +
> ssize_t inet_sendpage(struct socket *sock, struct page *page, int offset,
> size_t size, int flags)
> {
> @@ -1050,6 +1065,7 @@ const struct proto_ops inet_stream_ops = {
> #ifdef CONFIG_MMU
> .mmap = tcp_mmap,
> #endif
> + .splice_eof = inet_splice_eof,
> .sendpage = inet_sendpage,
> .splice_read = tcp_splice_read,
> .read_sock = tcp_read_sock,
> @@ -1084,6 +1100,7 @@ const struct proto_ops inet_dgram_ops = {
> .read_skb = udp_read_skb,
> .recvmsg = inet_recvmsg,
> .mmap = sock_no_mmap,
> + .splice_eof = inet_splice_eof,
> .sendpage = inet_sendpage,
> .set_peek_off = sk_set_peek_off,
> #ifdef CONFIG_COMPAT
> @@ -1115,6 +1132,7 @@ static const struct proto_ops inet_sockraw_ops = {
> .sendmsg = inet_sendmsg,
> .recvmsg = inet_recvmsg,
> .mmap = sock_no_mmap,
> + .splice_eof = inet_splice_eof,
> .sendpage = inet_sendpage,
> #ifdef CONFIG_COMPAT
> .compat_ioctl = inet_compat_ioctl,
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 53b7751b68e1..09f03221a6f1 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -1371,6 +1371,22 @@ int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
> }
> EXPORT_SYMBOL(tcp_sendmsg);
>
> +void tcp_splice_eof(struct socket *sock)
> +{
> + struct sock *sk = sock->sk;
> + struct tcp_sock *tp = tcp_sk(sk);
> + int mss_now, size_goal;
> +
> + if (!tcp_write_queue_tail(sk))
> + return;
> +
> + lock_sock(sk);
> + mss_now = tcp_send_mss(sk, &size_goal, 0);
> + tcp_push(sk, 0, mss_now, tp->nonagle, size_goal);
> + release_sock(sk);
> +}
> +EXPORT_SYMBOL_GPL(tcp_splice_eof);
> +
> /*
> * Handle reading urgent data. BSD has very simple semantics for
> * this, no blocking and very strange errors 8)
> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index 53e9ce2f05bb..84a5d557dc1a 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -3116,6 +3116,7 @@ struct proto tcp_prot = {
> .keepalive = tcp_set_keepalive,
> .recvmsg = tcp_recvmsg,
> .sendmsg = tcp_sendmsg,
> + .splice_eof = tcp_splice_eof,
> .sendpage = tcp_sendpage,
> .backlog_rcv = tcp_v4_do_rcv,
> .release_cb = tcp_release_cb,
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index fd3dae081f3a..df5e407286d7 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -1324,6 +1324,21 @@ int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
> }
> EXPORT_SYMBOL(udp_sendmsg);
>
> +void udp_splice_eof(struct socket *sock)
> +{
> + struct sock *sk = sock->sk;
> + struct udp_sock *up = udp_sk(sk);
> +
> + if (!up->pending || READ_ONCE(up->corkflag))
> + return;
> +
> + lock_sock(sk);
> + if (up->pending && !READ_ONCE(up->corkflag))
> + udp_push_pending_frames(sk);
> + release_sock(sk);
> +}
> +EXPORT_SYMBOL_GPL(udp_splice_eof);
> +
> int udp_sendpage(struct sock *sk, struct page *page, int offset,
> size_t size, int flags)
> {
> @@ -2918,6 +2933,7 @@ struct proto udp_prot = {
> .getsockopt = udp_getsockopt,
> .sendmsg = udp_sendmsg,
> .recvmsg = udp_recvmsg,
> + .splice_eof = udp_splice_eof,
> .sendpage = udp_sendpage,
> .release_cb = ip4_datagram_release_cb,
> .hash = udp_lib_hash,
> diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
> index 2bbf13216a3d..564942bee067 100644
> --- a/net/ipv6/af_inet6.c
> +++ b/net/ipv6/af_inet6.c
> @@ -695,6 +695,7 @@ const struct proto_ops inet6_stream_ops = {
> #ifdef CONFIG_MMU
> .mmap = tcp_mmap,
> #endif
> + .splice_eof = inet_splice_eof,
> .sendpage = inet_sendpage,
> .sendmsg_locked = tcp_sendmsg_locked,
> .sendpage_locked = tcp_sendpage_locked,
> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index d657713d1c71..c17c8ff94b79 100644
> --- a/net/ipv6/tcp_ipv6.c
> +++ b/net/ipv6/tcp_ipv6.c
> @@ -2150,6 +2150,7 @@ struct proto tcpv6_prot = {
> .keepalive = tcp_set_keepalive,
> .recvmsg = tcp_recvmsg,
> .sendmsg = tcp_sendmsg,
> + .splice_eof = tcp_splice_eof,
> .sendpage = tcp_sendpage,
> .backlog_rcv = tcp_v6_do_rcv,
> .release_cb = tcp_release_cb,
> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
> index e5a337e6b970..6c5975b13ae3 100644
> --- a/net/ipv6/udp.c
> +++ b/net/ipv6/udp.c
> @@ -1653,6 +1653,23 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
> }
> EXPORT_SYMBOL(udpv6_sendmsg);
>
> +static void udpv6_splice_eof(struct socket *sock)
> +{
> + struct sock *sk = sock->sk;
> + struct udp_sock *up = udp_sk(sk);
> +
> + if (!up->pending || READ_ONCE(up->corkflag))
> + return;
> +
> + if (up->pending == AF_INET)
> + udp_splice_eof(sock);

Do we need this ?

> +
> + lock_sock(sk);
> + if (up->pending && !READ_ONCE(up->corkflag))
> + udp_push_pending_frames(sk);

We should use udp_v6_push_pending_frames(sk) as up->pending
could be AF_INET even after the test above.

> + release_sock(sk);
> +}
> +
> void udpv6_destroy_sock(struct sock *sk)
> {
> struct udp_sock *up = udp_sk(sk);
> @@ -1764,6 +1781,7 @@ struct proto udpv6_prot = {
> .getsockopt = udpv6_getsockopt,
> .sendmsg = udpv6_sendmsg,
> .recvmsg = udpv6_recvmsg,
> + .splice_eof = udpv6_splice_eof,
> .release_cb = ip6_datagram_release_cb,
> .hash = udp_lib_hash,
> .unhash = udp_lib_unhash,

Next message: Aleksandr Mikhalitsyn: "Re: [PATCH v3 03/14] ceph: handle idmapped mounts in create_request_message()"
Previous message: Enric Balletbo i Serra: "[PATCH v3] selftests/input: Introduce basic tests for evdev ioctls"
In reply to: David Howells: "[PATCH net-next v5 07/14] ipv4, ipv6: Use splice_eof() to flush"
Next in thread: David Howells: "Re: [PATCH net-next v5 07/14] ipv4, ipv6: Use splice_eof() to flush"
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