sock: Introduce SO_RCVPRIORITY socket option

Add new socket option, SO_RCVPRIORITY, to include SO_PRIORITY in the
ancillary data returned by recvmsg().
This is analogous to the existing support for SO_RCVMARK,
as implemented in commit 6fd1d51cfa ("net: SO_RCVMARK socket option
for SO_MARK with recvmsg()").

Reviewed-by: Willem de Bruijn <willemb@google.com>
Suggested-by: Ferenc Fejes <fejes@inf.elte.hu>
Signed-off-by: Anna Emese Nyiri <annaemesenyiri@gmail.com>
Link: https://patch.msgid.link/20241213084457.45120-5-annaemesenyiri@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

arch/alpha/include/uapi/asm/socket.h

@@ -148,6 +148,8 @@
 
 #define SCM_TS_OPT_ID		81
 
+#define SO_RCVPRIORITY		82
+
 #if !defined(__KERNEL__)
 
 #if __BITS_PER_LONG == 64

arch/mips/include/uapi/asm/socket.h

@@ -159,6 +159,8 @@
 
 #define SCM_TS_OPT_ID		81
 
+#define SO_RCVPRIORITY		82
+
 #if !defined(__KERNEL__)
 
 #if __BITS_PER_LONG == 64

arch/parisc/include/uapi/asm/socket.h

@@ -140,6 +140,8 @@
 
 #define SCM_TS_OPT_ID		0x404C
 
+#define SO_RCVPRIORITY		0x404D
+
 #if !defined(__KERNEL__)
 
 #if __BITS_PER_LONG == 64

arch/sparc/include/uapi/asm/socket.h

@@ -141,6 +141,8 @@
 
 #define SCM_TS_OPT_ID            0x005a
 
+#define SO_RCVPRIORITY           0x005b
+
 #if !defined(__KERNEL__)
 
 

include/net/sock.h

@@ -953,6 +953,7 @@ enum sock_flags {
 	SOCK_XDP, /* XDP is attached */
 	SOCK_TSTAMP_NEW, /* Indicates 64 bit timestamps always */
 	SOCK_RCVMARK, /* Receive SO_MARK  ancillary data with packet */
+	SOCK_RCVPRIORITY, /* Receive SO_PRIORITY ancillary data with packet */
 };
 
 #define SK_FLAGS_TIMESTAMP ((1UL << SOCK_TIMESTAMP) | (1UL << SOCK_TIMESTAMPING_RX_SOFTWARE))
@@ -2660,7 +2661,8 @@ static inline void sock_recv_cmsgs(struct msghdr *msg, struct sock *sk,
 {
 #define FLAGS_RECV_CMSGS ((1UL << SOCK_RXQ_OVFL)			| \
 			   (1UL << SOCK_RCVTSTAMP)			| \
-			   (1UL << SOCK_RCVMARK))
+			   (1UL << SOCK_RCVMARK)			|\
+			   (1UL << SOCK_RCVPRIORITY))
 #define TSFLAGS_ANY	  (SOF_TIMESTAMPING_SOFTWARE			| \
 			   SOF_TIMESTAMPING_RAW_HARDWARE)
 

include/uapi/asm-generic/socket.h

@@ -143,6 +143,8 @@
 
 #define SCM_TS_OPT_ID		81
 
+#define SO_RCVPRIORITY		82
+
 #if !defined(__KERNEL__)
 
 #if __BITS_PER_LONG == 64 || (defined(__x86_64__) && defined(__ILP32__))

net/core/sock.c

@@ -1519,6 +1519,10 @@ int sk_setsockopt(struct sock *sk, int level, int optname,
 		sock_valbool_flag(sk, SOCK_RCVMARK, valbool);
 		break;
 
+	case SO_RCVPRIORITY:
+		sock_valbool_flag(sk, SOCK_RCVPRIORITY, valbool);
+		break;
+
 	case SO_RXQ_OVFL:
 		sock_valbool_flag(sk, SOCK_RXQ_OVFL, valbool);
 		break;
@@ -1947,6 +1951,10 @@ int sk_getsockopt(struct sock *sk, int level, int optname,
 		v.val = sock_flag(sk, SOCK_RCVMARK);
 		break;
 
+	case SO_RCVPRIORITY:
+		v.val = sock_flag(sk, SOCK_RCVPRIORITY);
+		break;
+
 	case SO_RXQ_OVFL:
 		v.val = sock_flag(sk, SOCK_RXQ_OVFL);
 		break;

net/socket.c

@@ -1008,12 +1008,23 @@ static void sock_recv_mark(struct msghdr *msg, struct sock *sk,
 	}
 }
 
+static void sock_recv_priority(struct msghdr *msg, struct sock *sk,
+			       struct sk_buff *skb)
+{
+	if (sock_flag(sk, SOCK_RCVPRIORITY) && skb) {
+		__u32 priority = skb->priority;
+
+		put_cmsg(msg, SOL_SOCKET, SO_PRIORITY, sizeof(__u32), &priority);
+	}
+}
+
 void __sock_recv_cmsgs(struct msghdr *msg, struct sock *sk,
 		       struct sk_buff *skb)
 {
 	sock_recv_timestamp(msg, sk, skb);
 	sock_recv_drops(msg, sk, skb);
 	sock_recv_mark(msg, sk, skb);
+	sock_recv_priority(msg, sk, skb);
 }
 EXPORT_SYMBOL_GPL(__sock_recv_cmsgs);
 

tools/include/uapi/asm-generic/socket.h

@@ -126,6 +126,8 @@
 
 #define SCM_TS_OPT_ID		78
 
+#define SO_RCVPRIORITY		79
+
 #if !defined(__KERNEL__)
 
 #if __BITS_PER_LONG == 64 || (defined(__x86_64__) && defined(__ILP32__))