udp: Remove UDPLITE_SEND_CSCOV and UDPLITE_RECV_CSCOV.

UDP-Lite supports variable-length checksum and has two socket
options, UDPLITE_SEND_CSCOV and UDPLITE_RECV_CSCOV, to control
the checksum coverage.

Let's remove the support.

setsockopt(UDPLITE_SEND_CSCOV / UDPLITE_RECV_CSCOV) was only
available for UDP-Lite and returned -ENOPROTOOPT for UDP.

Now, the options are handled in ip_setsockopt() and
ipv6_setsockopt(), which still return the same error.

getsockopt(UDPLITE_SEND_CSCOV / UDPLITE_RECV_CSCOV) was available
for UDP and always returned 0, meaning full checksum, but now
-ENOPROTOOPT is returned.

Given that getsockopt() is meaningless for UDP and even the options
are not defined under include/uapi/, this should not be a problem.

  $ man 7 udplite
  ...
  BUGS
       Where glibc support is missing, the following definitions
       are needed:

           #define IPPROTO_UDPLITE     136
           #define UDPLITE_SEND_CSCOV  10
           #define UDPLITE_RECV_CSCOV  11

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260311052020.1213705-10-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

6 files changed, 8 insertions, 72 deletions

diff --git a/include/linux/udp.h b/include/linux/udp.h
index 1cbf6b4d3aab..ce56ebcee5cb 100644
--- a/include/linux/udp.h
+++ b/include/linux/udp.h
@@ -40,8 +40,6 @@ enum {
 	UDP_FLAGS_ACCEPT_FRAGLIST,
 	UDP_FLAGS_ACCEPT_L4,
 	UDP_FLAGS_ENCAP_ENABLED, /* This socket enabled encap */
-	UDP_FLAGS_UDPLITE_SEND_CC, /* set via udplite setsockopt */
-	UDP_FLAGS_UDPLITE_RECV_CC, /* set via udplite setsockopt */
 };
 
 /* per NUMA structure for lockless producer usage. */
@@ -74,11 +72,7 @@ struct udp_sock {
 	 */
 	__u16		 len;		/* total length of pending frames */
 	__u16		 gso_size;
-	/*
-	 * Fields specific to UDP-Lite.
-	 */
-	__u16		 pcslen;
-	__u16		 pcrlen;
+
 	/*
 	 * For encapsulation sockets.
 	 */
@@ -236,8 +230,6 @@ static inline void udp_allow_gso(struct sock *sk)
 	hlist_nulls_for_each_entry_rcu(__up, node, list, udp_lrpa_node)
 #endif
 
-#define IS_UDPLITE(__sk) (unlikely(__sk->sk_protocol == IPPROTO_UDPLITE))
-
 static inline struct sock *udp_tunnel_sk(const struct net *net, bool is_ipv6)
 {
 #if IS_ENABLED(CONFIG_NET_UDP_TUNNEL)
diff --git a/include/net/udplite.h b/include/net/udplite.h
deleted file mode 100644
index 6bfa1d6833d1..000000000000
--- a/include/net/udplite.h
+++ /dev/null
@@ -1,15 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- *	Definitions for the UDP-Lite (RFC 3828) code.
- */
-#ifndef _UDPLITE_H
-#define _UDPLITE_H
-
-#include <net/ip6_checksum.h>
-#include <net/udp.h>
-
-/* UDP-Lite socket options */
-#define UDPLITE_SEND_CSCOV   10 /* sender partial coverage (as sent)      */
-#define UDPLITE_RECV_CSCOV   11 /* receiver partial coverage (threshold ) */
-
-#endif	/* _UDPLITE_H */
diff --git a/include/uapi/linux/udp.h b/include/uapi/linux/udp.h
index edca3e430305..877fb02df8fb 100644
--- a/include/uapi/linux/udp.h
+++ b/include/uapi/linux/udp.h
@@ -29,6 +29,8 @@ struct udphdr {
 
 /* UDP socket options */
 #define UDP_CORK	1	/* Never send partially complete segments */
+/* Deprecated, reserved for UDPLITE_SEND_CSCOV 10 */
+/* Deprecated, reserved for UDPLITE_RECV_CSCOV 11 */
 #define UDP_ENCAP	100	/* Set the socket to accept encapsulated packets */
 #define UDP_NO_CHECK6_TX 101	/* Disable sending checksum for UDP6X */
 #define UDP_NO_CHECK6_RX 102	/* Disable accepting checksum for UDP6 */
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 9a2c8ff96e83..d47ca721ef0d 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -117,7 +117,6 @@
 #include <net/sock_reuseport.h>
 #include <net/addrconf.h>
 #include <net/udp_tunnel.h>
-#include <net/udplite.h>
 #include <net/gro.h>
 #if IS_ENABLED(CONFIG_IPV6)
 #include <net/ipv6_stubs.h>
@@ -2924,7 +2923,6 @@ int udp_lib_setsockopt(struct sock *sk, int level, int optname,
 	struct udp_sock *up = udp_sk(sk);
 	int val, valbool;
 	int err = 0;
-	int is_udplite = IS_UDPLITE(sk);
 
 	if (level == SOL_SOCKET) {
 		err = sk_setsockopt(sk, level, optname, optval, optlen);
@@ -3011,36 +3009,6 @@ int udp_lib_setsockopt(struct sock *sk, int level, int optname,
 		sockopt_release_sock(sk);
 		break;
 
-	/*
-	 * 	UDP-Lite's partial checksum coverage (RFC 3828).
-	 */
-	/* The sender sets actual checksum coverage length via this option.
-	 * The case coverage > packet length is handled by send module. */
-	case UDPLITE_SEND_CSCOV:
-		if (!is_udplite)         /* Disable the option on UDP sockets */
-			return -ENOPROTOOPT;
-		if (val != 0 && val < 8) /* Illegal coverage: use default (8) */
-			val = 8;
-		else if (val > USHRT_MAX)
-			val = USHRT_MAX;
-		WRITE_ONCE(up->pcslen, val);
-		udp_set_bit(UDPLITE_SEND_CC, sk);
-		break;
-
-	/* The receiver specifies a minimum checksum coverage value. To make
-	 * sense, this should be set to at least 8 (as done below). If zero is
-	 * used, this again means full checksum coverage.                     */
-	case UDPLITE_RECV_CSCOV:
-		if (!is_udplite)         /* Disable the option on UDP sockets */
-			return -ENOPROTOOPT;
-		if (val != 0 && val < 8) /* Avoid silly minimal values.       */
-			val = 8;
-		else if (val > USHRT_MAX)
-			val = USHRT_MAX;
-		WRITE_ONCE(up->pcrlen, val);
-		udp_set_bit(UDPLITE_RECV_CC, sk);
-		break;
-
 	default:
 		err = -ENOPROTOOPT;
 		break;
@@ -3053,7 +3021,7 @@ EXPORT_IPV6_MOD(udp_lib_setsockopt);
 static int udp_setsockopt(struct sock *sk, int level, int optname, sockptr_t optval,
 			  unsigned int optlen)
 {
-	if (level == SOL_UDP  ||  level == SOL_UDPLITE || level == SOL_SOCKET)
+	if (level == SOL_UDP || level == SOL_SOCKET)
 		return udp_lib_setsockopt(sk, level, optname,
 					  optval, optlen,
 					  udp_push_pending_frames);
@@ -3099,16 +3067,6 @@ int udp_lib_getsockopt(struct sock *sk, int level, int optname,
 		val = udp_test_bit(GRO_ENABLED, sk);
 		break;
 
-	/* The following two cannot be changed on UDP sockets, the return is
-	 * always 0 (which corresponds to the full checksum coverage of UDP). */
-	case UDPLITE_SEND_CSCOV:
-		val = READ_ONCE(up->pcslen);
-		break;
-
-	case UDPLITE_RECV_CSCOV:
-		val = READ_ONCE(up->pcrlen);
-		break;
-
 	default:
 		return -ENOPROTOOPT;
 	}
@@ -3124,7 +3082,7 @@ EXPORT_IPV6_MOD(udp_lib_getsockopt);
 static int udp_getsockopt(struct sock *sk, int level, int optname,
 			  char __user *optval, int __user *optlen)
 {
-	if (level == SOL_UDP  ||  level == SOL_UDPLITE)
+	if (level == SOL_UDP)
 		return udp_lib_getsockopt(sk, level, optname, optval, optlen);
 	return ip_getsockopt(sk, level, optname, optval, optlen);
 }
diff --git a/net/ipv6/ip6_checksum.c b/net/ipv6/ip6_checksum.c
index 8bb68a0cdfd6..e1a594873675 100644
--- a/net/ipv6/ip6_checksum.c
+++ b/net/ipv6/ip6_checksum.c
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <net/ip.h>
+#include <net/ip6_checksum.h>
 #include <net/udp.h>
-#include <net/udplite.h>
 #include <asm/checksum.h>
 
 #ifndef _HAVE_ARCH_IPV6_CSUM
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 511e3f898be5..c3d8b5ede164 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -58,7 +58,6 @@
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
 #include <trace/events/skb.h>
-#include <net/udplite.h>
 
 static void udpv6_destruct_sock(struct sock *sk)
 {
@@ -1831,7 +1830,7 @@ static void udpv6_destroy_sock(struct sock *sk)
 static int udpv6_setsockopt(struct sock *sk, int level, int optname,
 			    sockptr_t optval, unsigned int optlen)
 {
-	if (level == SOL_UDP  ||  level == SOL_UDPLITE || level == SOL_SOCKET)
+	if (level == SOL_UDP || level == SOL_SOCKET)
 		return udp_lib_setsockopt(sk, level, optname,
 					  optval, optlen,
 					  udp_v6_push_pending_frames);
@@ -1841,7 +1840,7 @@ static int udpv6_setsockopt(struct sock *sk, int level, int optname,
 static int udpv6_getsockopt(struct sock *sk, int level, int optname,
 			    char __user *optval, int __user *optlen)
 {
-	if (level == SOL_UDP  ||  level == SOL_UDPLITE)
+	if (level == SOL_UDP)
 		return udp_lib_getsockopt(sk, level, optname, optval, optlen);
 	return ipv6_getsockopt(sk, level, optname, optval, optlen);
 }