1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 *	Definitions for the UDP-Lite (RFC 3828) code.
4 */
5#ifndef _UDPLITE_H
6#define _UDPLITE_H
7
8#include <net/ip6_checksum.h>
9#include <net/udp.h>
10
11/* UDP-Lite socket options */
12#define UDPLITE_SEND_CSCOV   10 /* sender partial coverage (as sent)      */
13#define UDPLITE_RECV_CSCOV   11 /* receiver partial coverage (threshold ) */
14
15extern struct proto 		udplite_prot;
16extern struct udp_table		udplite_table;
17
18/*
19 *	Checksum computation is all in software, hence simpler getfrag.
20 */
21static __inline__ int udplite_getfrag(void *from, char *to, int  offset,
22				      int len, int odd, struct sk_buff *skb)
23{
24	struct msghdr *msg = from;
25	return copy_from_iter_full(to, len, &msg->msg_iter) ? 0 : -EFAULT;
26}
27
28/*
29 * 	Checksumming routines
30 */
31static inline int udplite_checksum_init(struct sk_buff *skb, struct udphdr *uh)
32{
33	u16 cscov;
34
35        /* In UDPv4 a zero checksum means that the transmitter generated no
36         * checksum. UDP-Lite (like IPv6) mandates checksums, hence packets
37         * with a zero checksum field are illegal.                            */
38	if (uh->check == 0) {
39		net_dbg_ratelimited("UDPLite: zeroed checksum field\n");
40		return 1;
41	}
42
43	cscov = ntohs(uh->len);
44
45	if (cscov == 0)		 /* Indicates that full coverage is required. */
46		;
47	else if (cscov < 8  || cscov > skb->len) {
48		/*
49		 * Coverage length violates RFC 3828: log and discard silently.
50		 */
51		net_dbg_ratelimited("UDPLite: bad csum coverage %d/%d\n",
52				    cscov, skb->len);
53		return 1;
54
55	} else if (cscov < skb->len) {
56        	UDP_SKB_CB(skb)->partial_cov = 1;
57		UDP_SKB_CB(skb)->cscov = cscov;
58		if (skb->ip_summed == CHECKSUM_COMPLETE)
59			skb->ip_summed = CHECKSUM_NONE;
60		skb->csum_valid = 0;
61        }
62
63	return 0;
64}
65
66/* Fast-path computation of checksum. Socket may not be locked. */
67static inline __wsum udplite_csum(struct sk_buff *skb)
68{
69	const int off = skb_transport_offset(skb);
70	const struct sock *sk = skb->sk;
71	int len = skb->len - off;
72
73	if (udp_test_bit(UDPLITE_SEND_CC, sk)) {
74		u16 pcslen = READ_ONCE(udp_sk(sk)->pcslen);
75
76		if (pcslen < len) {
77			if (pcslen > 0)
78				len = pcslen;
79			udp_hdr(skb)->len = htons(pcslen);
80		}
81	}
82	skb->ip_summed = CHECKSUM_NONE;     /* no HW support for checksumming */
83
84	return skb_checksum(skb, off, len, 0);
85}
86
87void udplite4_register(void);
88#endif	/* _UDPLITE_H */
89