[PATCH net-next v4 11/27] tcp: support externally provided ubufs

Pavel Begunkov
2022-07-07T11:52:23Z

Teach ipv4/udp how to use external ubuf_info provided in msghdr and
also prepare it for managed frags by sprinkling
skb_zcopy_downgrade_managed() when it could mix managed and not managed
frags.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
net/ipv4/tcp.c | 32 ++++++++++++++++++++------------
1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 390eb3dc53bd..a81f694af5e9 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1223,17 +1223,23 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)

flags = msg->msg_flags;

- if (flags & MSG_ZEROCOPY && size && sock_flag(sk, SOCK_ZEROCOPY)) {
+ if ((flags & MSG_ZEROCOPY) && size) {
skb = tcp_write_queue_tail(sk);
- uarg = msg_zerocopy_realloc(sk, size, skb_zcopy(skb));
- if (!uarg) {
- err = -ENOBUFS;
- goto out_err;
- }

- zc = sk->sk_route_caps & NETIF_F_SG;
- if (!zc)
- uarg->zerocopy = 0;
+ if (msg->msg_ubuf) {
+ uarg = msg->msg_ubuf;
+ net_zcopy_get(uarg);
+ zc = sk->sk_route_caps & NETIF_F_SG;
+ } else if (sock_flag(sk, SOCK_ZEROCOPY)) {
+ uarg = msg_zerocopy_realloc(sk, size, skb_zcopy(skb));
+ if (!uarg) {
+ err = -ENOBUFS;
+ goto out_err;
+ }
+ zc = sk->sk_route_caps & NETIF_F_SG;
+ if (!zc)
+ uarg->zerocopy = 0;
+ }
}

if (unlikely(flags & MSG_FASTOPEN || inet_sk(sk)->defer_connect) &&
@@ -1356,9 +1362,11 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)

copy = min_t(int, copy, pfrag->size - pfrag->offset);

- if (tcp_downgrade_zcopy_pure(sk, skb))
- goto wait_for_space;
-
+ if (unlikely(skb_zcopy_pure(skb) || skb_zcopy_managed(skb))) {
+ if (tcp_downgrade_zcopy_pure(sk, skb))
+ goto wait_for_space;
+ skb_zcopy_downgrade_managed(skb);
+ }
copy = tcp_wmem_schedule(sk, copy);
if (!copy)
goto wait_for_space;
--
2.36.1