netdev - [Patch bpf-next v3 02/10] af_unix: implement ->read

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Message-Id: <20210426025001.7899-3-xiyou.wangcong@gmail.com>
Date:   Sun, 25 Apr 2021 19:49:53 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     netdev@...r.kernel.org
Cc:     bpf@...r.kernel.org, jiang.wang@...edance.com,
        duanxiongchun@...edance.com, wangdongdong.6@...edance.com,
        Cong Wang <cong.wang@...edance.com>,
        John Fastabend <john.fastabend@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Lorenz Bauer <lmb@...udflare.com>
Subject: [Patch bpf-next v3 02/10] af_unix: implement ->read_sock() for sockmap

From: Cong Wang <cong.wang@...edance.com>

Implement ->read_sock() for AF_UNIX datagram socket, it is
pretty much similar to udp_read_sock().

Cc: John Fastabend <john.fastabend@...il.com>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: Jakub Sitnicki <jakub@...udflare.com>
Cc: Lorenz Bauer <lmb@...udflare.com>
Signed-off-by: Cong Wang <cong.wang@...edance.com>
---
 net/unix/af_unix.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 5a31307ceb76..f4dc22db371d 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -661,6 +661,8 @@ static ssize_t unix_stream_splice_read(struct socket *,  loff_t *ppos,
 				       unsigned int flags);
 static int unix_dgram_sendmsg(struct socket *, struct msghdr *, size_t);
 static int unix_dgram_recvmsg(struct socket *, struct msghdr *, size_t, int);
+static int unix_read_sock(struct sock *sk, read_descriptor_t *desc,
+			  sk_read_actor_t recv_actor);
 static int unix_dgram_connect(struct socket *, struct sockaddr *,
 			      int, int);
 static int unix_seqpacket_sendmsg(struct socket *, struct msghdr *, size_t);
@@ -738,6 +740,7 @@ static const struct proto_ops unix_dgram_ops = {
 	.listen =	sock_no_listen,
 	.shutdown =	unix_shutdown,
 	.sendmsg =	unix_dgram_sendmsg,
+	.read_sock =	unix_read_sock,
 	.recvmsg =	unix_dgram_recvmsg,
 	.mmap =		sock_no_mmap,
 	.sendpage =	sock_no_sendpage,
@@ -2183,6 +2186,41 @@ static int unix_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
 	return err;
 }
 
+static int unix_read_sock(struct sock *sk, read_descriptor_t *desc,
+			  sk_read_actor_t recv_actor)
+{
+	int copied = 0;
+
+	while (1) {
+		struct unix_sock *u = unix_sk(sk);
+		struct sk_buff *skb;
+		int used, err;
+
+		mutex_lock(&u->iolock);
+		skb = skb_recv_datagram(sk, 0, 1, &err);
+		if (!skb) {
+			mutex_unlock(&u->iolock);
+			return err;
+		}
+
+		used = recv_actor(desc, skb, 0, skb->len);
+		if (used <= 0) {
+			if (!copied)
+				copied = used;
+			mutex_unlock(&u->iolock);
+			break;
+		} else if (used <= skb->len) {
+			copied += used;
+		}
+		mutex_unlock(&u->iolock);
+
+		if (!desc->count)
+			break;
+	}
+
+	return copied;
+}
+
 /*
  *	Sleep until more data has arrived. But check for races..
  */
-- 
2.25.1