[Patch bpf 2/3] net: poll psock queues too for sockmap sockets

[Cong Wang <xiyou.wangcong@xxxxxxxxx>]

From: Cong Wang <cong.wang@xxxxxxxxxxxxx>

Yucong noticed we can't poll() sockets in sockmap even
when they are the destination sockets of redirections.
This is because we never poll any psock queues in ->poll().
We can not overwrite ->poll() as it is in struct proto_ops,
not in struct proto.

So introduce sk_msg_poll() to poll psock ingress_msg queue
and let sockets which support sockmap invoke it directly.

Reported-by: Yucong Sun <sunyucong@xxxxxxxxx>
Cc: John Fastabend <john.fastabend@xxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
Cc: Lorenz Bauer <lmb@xxxxxxxxxxxxxx>
Signed-off-by: Cong Wang <cong.wang@xxxxxxxxxxxxx>
---
 include/linux/skmsg.h |  6 ++++++
 net/core/skmsg.c      | 15 +++++++++++++++
 net/ipv4/tcp.c        |  2 ++
 net/ipv4/udp.c        |  2 ++
 net/unix/af_unix.c    |  5 +++++
 5 files changed, 30 insertions(+)

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index d47097f2c8c0..163b0cc1703a 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -128,6 +128,7 @@ int sk_msg_memcopy_from_iter(struct sock *sk, struct iov_iter *from,
 			     struct sk_msg *msg, u32 bytes);
 int sk_msg_recvmsg(struct sock *sk, struct sk_psock *psock, struct msghdr *msg,
 		   int len, int flags);
+__poll_t sk_msg_poll(struct sock *sk);
 
 static inline void sk_msg_check_to_free(struct sk_msg *msg, u32 i, u32 bytes)
 {
@@ -562,5 +563,10 @@ static inline void skb_bpf_redirect_clear(struct sk_buff *skb)
 {
 	skb->_sk_redir = 0;
 }
+#else
+static inline __poll_t sk_msg_poll(struct sock *sk)
+{
+	return 0;
+}
 #endif /* CONFIG_NET_SOCK_MSG */
 #endif /* _LINUX_SKMSG_H */
diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index 2d6249b28928..8e6d7ea43eca 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -474,6 +474,21 @@ int sk_msg_recvmsg(struct sock *sk, struct sk_psock *psock, struct msghdr *msg,
 }
 EXPORT_SYMBOL_GPL(sk_msg_recvmsg);
 
+__poll_t sk_msg_poll(struct sock *sk)
+{
+	struct sk_psock *psock;
+	__poll_t mask = 0;
+
+	psock = sk_psock_get_checked(sk);
+	if (IS_ERR_OR_NULL(psock))
+		return 0;
+	if (!sk_psock_queue_empty(psock))
+		mask |= EPOLLIN | EPOLLRDNORM;
+	sk_psock_put(sk, psock);
+	return mask;
+}
+EXPORT_SYMBOL_GPL(sk_msg_poll);
+
 static struct sk_msg *sk_psock_create_ingress_msg(struct sock *sk,
 						  struct sk_buff *skb)
 {
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index e8b48df73c85..2eb1a87ba056 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -280,6 +280,7 @@
 #include <linux/uaccess.h>
 #include <asm/ioctls.h>
 #include <net/busy_poll.h>
+#include <linux/skmsg.h>
 
 /* Track pending CMSGs. */
 enum {
@@ -563,6 +564,7 @@ __poll_t tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
 
 		if (tcp_stream_is_readable(sk, target))
 			mask |= EPOLLIN | EPOLLRDNORM;
+		mask |= sk_msg_poll(sk);
 
 		if (!(sk->sk_shutdown & SEND_SHUTDOWN)) {
 			if (__sk_stream_is_writeable(sk, 1)) {
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 8851c9463b4b..fbc989d27388 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -97,6 +97,7 @@
 #include <linux/skbuff.h>
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
+#include <linux/skmsg.h>
 #include <net/net_namespace.h>
 #include <net/icmp.h>
 #include <net/inet_hashtables.h>
@@ -2866,6 +2867,7 @@ __poll_t udp_poll(struct file *file, struct socket *sock, poll_table *wait)
 	    !(sk->sk_shutdown & RCV_SHUTDOWN) && first_packet_length(sk) == -1)
 		mask &= ~(EPOLLIN | EPOLLRDNORM);
 
+	mask |= sk_msg_poll(sk);
 	return mask;
 
 }
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 92345c9bb60c..5d705541d082 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -114,6 +114,7 @@
 #include <linux/freezer.h>
 #include <linux/file.h>
 #include <linux/btf_ids.h>
+#include <linux/skmsg.h>
 
 #include "scm.h"
 
@@ -3015,6 +3016,8 @@ static __poll_t unix_poll(struct file *file, struct socket *sock, poll_table *wa
 	if (!skb_queue_empty_lockless(&sk->sk_receive_queue))
 		mask |= EPOLLIN | EPOLLRDNORM;
 
+	mask |= sk_msg_poll(sk);
+
 	/* Connection-based need to check for termination and startup */
 	if ((sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET) &&
 	    sk->sk_state == TCP_CLOSE)
@@ -3054,6 +3057,8 @@ static __poll_t unix_dgram_poll(struct file *file, struct socket *sock,
 	if (!skb_queue_empty_lockless(&sk->sk_receive_queue))
 		mask |= EPOLLIN | EPOLLRDNORM;
 
+	mask |= sk_msg_poll(sk);
+
 	/* Connection-based need to check for termination and startup */
 	if (sk->sk_type == SOCK_SEQPACKET) {
 		if (sk->sk_state == TCP_CLOSE)
-- 
2.30.2