udp: Remove partial csum code in TX.

UDP TX paths also have some code for UDP-Lite partial
checksum:

  * udplite_csum() in udp_send_skb() and udp_v6_send_skb()
  * udplite_getfrag() in udp_sendmsg() and udpv6_sendmsg()

Let's remove such code.

Now, we can use IPPROTO_UDP directly instead of sk->sk_protocol
or fl6->flowi6_proto for csum_tcpudp_magic() and csum_ipv6_magic().

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260311052020.1213705-9-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 22 insertions, 36 deletions

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index d42fb9330c22..9a2c8ff96e83 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1120,20 +1120,19 @@ static int udp_send_skb(struct sk_buff *skb, struct flowi4 *fl4,
 			struct inet_cork *cork)
 {
 	struct sock *sk = skb->sk;
-	struct inet_sock *inet = inet_sk(sk);
+	int offset, len, datalen;
 	struct udphdr *uh;
 	int err;
-	int is_udplite = IS_UDPLITE(sk);
-	int offset = skb_transport_offset(skb);
-	int len = skb->len - offset;
-	int datalen = len - sizeof(*uh);
-	__wsum csum = 0;
+
+	offset = skb_transport_offset(skb);
+	len = skb->len - offset;
+	datalen = len - sizeof(*uh);
 
 	/*
 	 * Create a UDP header
 	 */
 	uh = udp_hdr(skb);
-	uh->source = inet->inet_sport;
+	uh->source = inet_sk(sk)->inet_sport;
 	uh->dest = fl4->fl4_dport;
 	uh->len = htons(len);
 	uh->check = 0;
@@ -1154,7 +1153,7 @@ static int udp_send_skb(struct sk_buff *skb, struct flowi4 *fl4,
 			kfree_skb(skb);
 			return -EINVAL;
 		}
-		if (is_udplite || dst_xfrm(skb_dst(skb))) {
+		if (dst_xfrm(skb_dst(skb))) {
 			kfree_skb(skb);
 			return -EIO;
 		}
@@ -1170,26 +1169,18 @@ static int udp_send_skb(struct sk_buff *skb, struct flowi4 *fl4,
 		}
 	}
 
-	if (is_udplite)  				 /*     UDP-Lite      */
-		csum = udplite_csum(skb);
-
-	else if (sk->sk_no_check_tx) {			 /* UDP csum off */
-
+	if (sk->sk_no_check_tx) {			 /* UDP csum off */
 		skb->ip_summed = CHECKSUM_NONE;
 		goto send;
-
 	} else if (skb->ip_summed == CHECKSUM_PARTIAL) { /* UDP hardware csum */
 csum_partial:
-
 		udp4_hwcsum(skb, fl4->saddr, fl4->daddr);
 		goto send;
-
-	} else
-		csum = udp_csum(skb);
+	}
 
 	/* add protocol-dependent pseudo-header */
 	uh->check = csum_tcpudp_magic(fl4->saddr, fl4->daddr, len,
-				      sk->sk_protocol, csum);
+				      IPPROTO_UDP, udp_csum(skb));
 	if (uh->check == 0)
 		uh->check = CSUM_MANGLED_0;
 
@@ -1270,26 +1261,23 @@ EXPORT_IPV6_MOD_GPL(udp_cmsg_send);
 
 int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 {
+	int corkreq = udp_test_bit(CORK, sk) || msg->msg_flags & MSG_MORE;
 	DEFINE_RAW_FLEX(struct ip_options_rcu, opt_copy, opt.__data,
 			IP_OPTIONS_DATA_FIXED_SIZE);
+	DECLARE_SOCKADDR(struct sockaddr_in *, usin, msg->msg_name);
+	int ulen = len, free = 0, connected = 0;
 	struct inet_sock *inet = inet_sk(sk);
 	struct udp_sock *up = udp_sk(sk);
-	DECLARE_SOCKADDR(struct sockaddr_in *, usin, msg->msg_name);
+	__be32 daddr, faddr, saddr;
+	struct rtable *rt = NULL;
 	struct flowi4 fl4_stack;
-	struct flowi4 *fl4;
-	int ulen = len;
 	struct ipcm_cookie ipc;
-	struct rtable *rt = NULL;
-	int free = 0;
-	int connected = 0;
-	__be32 daddr, faddr, saddr;
-	u8 scope;
-	__be16 dport;
-	int err, is_udplite = IS_UDPLITE(sk);
-	int corkreq = udp_test_bit(CORK, sk) || msg->msg_flags & MSG_MORE;
-	int (*getfrag)(void *, char *, int, int, int, struct sk_buff *);
 	struct sk_buff *skb;
+	struct flowi4 *fl4;
+	__be16 dport;
 	int uc_index;
+	u8 scope;
+	int err;
 
 	if (len > 0xFFFF)
 		return -EMSGSIZE;
@@ -1301,8 +1289,6 @@ int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	if (msg->msg_flags & MSG_OOB) /* Mirror BSD error message compatibility */
 		return -EOPNOTSUPP;
 
-	getfrag = is_udplite ? udplite_getfrag : ip_generic_getfrag;
-
 	fl4 = &inet->cork.fl.u.ip4;
 	if (READ_ONCE(up->pending)) {
 		/*
@@ -1444,7 +1430,7 @@ int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 
 		flowi4_init_output(fl4, ipc.oif, ipc.sockc.mark,
 				   ipc.tos & INET_DSCP_MASK, scope,
-				   sk->sk_protocol, flow_flags, faddr, saddr,
+				   IPPROTO_UDP, flow_flags, faddr, saddr,
 				   dport, inet->inet_sport,
 				   sk_uid(sk));
 
@@ -1478,7 +1464,7 @@ back_from_confirm:
 	if (!corkreq) {
 		struct inet_cork cork;
 
-		skb = ip_make_skb(sk, fl4, getfrag, msg, ulen,
+		skb = ip_make_skb(sk, fl4, ip_generic_getfrag, msg, ulen,
 				  sizeof(struct udphdr), &ipc, &rt,
 				  &cork, msg->msg_flags);
 		err = PTR_ERR(skb);
@@ -1509,7 +1495,7 @@ back_from_confirm:
 
 do_append_data:
 	up->len += ulen;
-	err = ip_append_data(sk, fl4, getfrag, msg, ulen,
+	err = ip_append_data(sk, fl4, ip_generic_getfrag, msg, ulen,
 			     sizeof(struct udphdr), &ipc, &rt,
 			     corkreq ? msg->msg_flags|MSG_MORE : msg->msg_flags);
 	if (err)