1/*
2 *	Definitions for the UDP-Lite (RFC 3828) code.
3 */
4#ifndef _UDPLITE_H
5#define _UDPLITE_H
6
7#include <net/ip6_checksum.h>
8
9/* UDP-Lite socket options */
10#define UDPLITE_SEND_CSCOV   10 /* sender partial coverage (as sent)      */
11#define UDPLITE_RECV_CSCOV   11 /* receiver partial coverage (threshold ) */
12
13extern struct proto 		udplite_prot;
14extern struct udp_table		udplite_table;
15
16/*
17 *	Checksum computation is all in software, hence simpler getfrag.
18 */
19static __inline__ int udplite_getfrag(void *from, char *to, int  offset,
20				      int len, int odd, struct sk_buff *skb)
21{
22	struct msghdr *msg = from;
23	return copy_from_iter(to, len, &msg->msg_iter) != len ? -EFAULT : 0;
24}
25
26/* Designate sk as UDP-Lite socket */
27static inline int udplite_sk_init(struct sock *sk)
28{
29	udp_sk(sk)->pcflag = UDPLITE_BIT;
30	return 0;
31}
32
33/*
34 * 	Checksumming routines
35 */
36static inline int udplite_checksum_init(struct sk_buff *skb, struct udphdr *uh)
37{
38	u16 cscov;
39
40        /* In UDPv4 a zero checksum means that the transmitter generated no
41         * checksum. UDP-Lite (like IPv6) mandates checksums, hence packets
42         * with a zero checksum field are illegal.                            */
43	if (uh->check == 0) {
44		net_dbg_ratelimited("UDPLite: zeroed checksum field\n");
45		return 1;
46	}
47
48	cscov = ntohs(uh->len);
49
50	if (cscov == 0)		 /* Indicates that full coverage is required. */
51		;
52	else if (cscov < 8  || cscov > skb->len) {
53		/*
54		 * Coverage length violates RFC 3828: log and discard silently.
55		 */
56		net_dbg_ratelimited("UDPLite: bad csum coverage %d/%d\n",
57				    cscov, skb->len);
58		return 1;
59
60	} else if (cscov < skb->len) {
61        	UDP_SKB_CB(skb)->partial_cov = 1;
62		UDP_SKB_CB(skb)->cscov = cscov;
63		if (skb->ip_summed == CHECKSUM_COMPLETE)
64			skb->ip_summed = CHECKSUM_NONE;
65        }
66
67	return 0;
68}
69
70/* Slow-path computation of checksum. Socket is locked. */
71static inline __wsum udplite_csum_outgoing(struct sock *sk, struct sk_buff *skb)
72{
73	const struct udp_sock *up = udp_sk(skb->sk);
74	int cscov = up->len;
75	__wsum csum = 0;
76
77	if (up->pcflag & UDPLITE_SEND_CC) {
78		/*
79		 * Sender has set `partial coverage' option on UDP-Lite socket.
80		 * The special case "up->pcslen == 0" signifies full coverage.
81		 */
82		if (up->pcslen < up->len) {
83			if (0 < up->pcslen)
84				cscov = up->pcslen;
85			udp_hdr(skb)->len = htons(up->pcslen);
86		}
87		/*
88		 * NOTE: Causes for the error case  `up->pcslen > up->len':
89		 *        (i)  Application error (will not be penalized).
90		 *       (ii)  Payload too big for send buffer: data is split
91		 *             into several packets, each with its own header.
92		 *             In this case (e.g. last segment), coverage may
93		 *             exceed packet length.
94		 *       Since packets with coverage length > packet length are
95		 *       illegal, we fall back to the defaults here.
96		 */
97	}
98
99	skb->ip_summed = CHECKSUM_NONE;     /* no HW support for checksumming */
100
101	skb_queue_walk(&sk->sk_write_queue, skb) {
102		const int off = skb_transport_offset(skb);
103		const int len = skb->len - off;
104
105		csum = skb_checksum(skb, off, (cscov > len)? len : cscov, csum);
106
107		if ((cscov -= len) <= 0)
108			break;
109	}
110	return csum;
111}
112
113/* Fast-path computation of checksum. Socket may not be locked. */
114static inline __wsum udplite_csum(struct sk_buff *skb)
115{
116	const struct udp_sock *up = udp_sk(skb->sk);
117	const int off = skb_transport_offset(skb);
118	int len = skb->len - off;
119
120	if ((up->pcflag & UDPLITE_SEND_CC) && up->pcslen < len) {
121		if (0 < up->pcslen)
122			len = up->pcslen;
123		udp_hdr(skb)->len = htons(up->pcslen);
124	}
125	skb->ip_summed = CHECKSUM_NONE;     /* no HW support for checksumming */
126
127	return skb_checksum(skb, off, len, 0);
128}
129
130void udplite4_register(void);
131int udplite_get_port(struct sock *sk, unsigned short snum,
132		     int (*scmp)(const struct sock *, const struct sock *));
133#endif	/* _UDPLITE_H */
134