[Patch bpf-next v2 1/9] af_unix: implement ->read_sock() for sockmap

[Cong Wang]

From: Cong Wang <cong.w...@bytedance.com>

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

Cc: John Fastabend <john.fastab...@gmail.com>
Cc: Daniel Borkmann <dan...@iogearbox.net>
Cc: Jakub Sitnicki <ja...@cloudflare.com>
Cc: Lorenz Bauer <l...@cloudflare.com>
Signed-off-by: Cong Wang <cong.w...@bytedance.com>
---
 net/unix/af_unix.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 5a31307ceb76..966359b64a56 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -661,6 +661,7 @@ 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);
+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 +739,7 @@ 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 +2185,41 @@ static int unix_dgram_recvmsg(struct socket *sock, 
struct msghdr *msg,
        return err;
 }
 
+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