netdev - [Patch bpf-next v4 07/11] udp: implement ->read

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Date:   Tue,  9 Mar 2021 21:32:18 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     netdev@...r.kernel.org
Cc:     bpf@...r.kernel.org, duanxiongchun@...edance.com,
        wangdongdong.6@...edance.com, jiang.wang@...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 v4 07/11] udp: implement ->read_sock() for sockmap

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

This is similar to tcp_read_sock(), except we do not need
to worry about connections, we just need to retrieve skb
from UDP receive queue.

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>
---
 include/net/udp.h   |  2 ++
 net/ipv4/af_inet.c  |  1 +
 net/ipv4/udp.c      | 35 +++++++++++++++++++++++++++++++++++
 net/ipv6/af_inet6.c |  1 +
 4 files changed, 39 insertions(+)

diff --git a/include/net/udp.h b/include/net/udp.h
index df7cc1edc200..347b62a753c3 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -329,6 +329,8 @@ struct sock *__udp6_lib_lookup(struct net *net,
 			       struct sk_buff *skb);
 struct sock *udp6_lib_lookup_skb(const struct sk_buff *skb,
 				 __be16 sport, __be16 dport);
+int udp_read_sock(struct sock *sk, read_descriptor_t *desc,
+		  sk_read_actor_t recv_actor);
 
 /* UDP uses skb->dev_scratch to cache as much information as possible and avoid
  * possibly multiple cache miss on dequeue()
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index a02ce89b56b5..915001f8000b 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1071,6 +1071,7 @@ const struct proto_ops inet_dgram_ops = {
 	.setsockopt	   = sock_common_setsockopt,
 	.getsockopt	   = sock_common_getsockopt,
 	.sendmsg	   = inet_sendmsg,
+	.read_sock	   = udp_read_sock,
 	.recvmsg	   = inet_recvmsg,
 	.mmap		   = sock_no_mmap,
 	.sendpage	   = inet_sendpage,
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 38952aaee3a1..a0adee3b1af4 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1782,6 +1782,41 @@ struct sk_buff *__skb_recv_udp(struct sock *sk, unsigned int flags,
 }
 EXPORT_SYMBOL(__skb_recv_udp);
 
+int udp_read_sock(struct sock *sk, read_descriptor_t *desc,
+		  sk_read_actor_t recv_actor)
+{
+	int copied = 0;
+
+	while (1) {
+		int offset = 0, err;
+		struct sk_buff *skb;
+
+		skb = __skb_recv_udp(sk, 0, 1, &offset, &err);
+		if (!skb)
+			break;
+		if (offset < skb->len) {
+			int used;
+			size_t len;
+
+			len = skb->len - offset;
+			used = recv_actor(desc, skb, offset, len);
+			if (used <= 0) {
+				if (!copied)
+					copied = used;
+				break;
+			} else if (used <= len) {
+				copied += used;
+				offset += used;
+			}
+		}
+		if (!desc->count)
+			break;
+	}
+
+	return copied;
+}
+EXPORT_SYMBOL(udp_read_sock);
+
 /*
  * 	This should be easy, if there is something there we
  * 	return it, otherwise we block.
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 1fb75f01756c..63218b0bcdb1 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -715,6 +715,7 @@ const struct proto_ops inet6_dgram_ops = {
 	.getsockopt	   = sock_common_getsockopt,	/* ok		*/
 	.sendmsg	   = inet6_sendmsg,		/* retpoline's sake */
 	.recvmsg	   = inet6_recvmsg,		/* retpoline's sake */
+	.read_sock	   = udp_read_sock,
 	.mmap		   = sock_no_mmap,
 	.sendpage	   = sock_no_sendpage,
 	.set_peek_off	   = sk_set_peek_off,
-- 
2.25.1