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 
10 /* UDP-Lite socket options */
11 #define UDPLITE_SEND_CSCOV   10 /* sender partial coverage (as sent)      */
12 #define UDPLITE_RECV_CSCOV   11 /* receiver partial coverage (threshold ) */
13 
14 extern struct proto 		udplite_prot;
15 extern struct udp_table		udplite_table;
16 
17 /*
18  *	Checksum computation is all in software, hence simpler getfrag.
19  */
udplite_getfrag(void * from,char * to,int offset,int len,int odd,struct sk_buff * skb)20 static __inline__ int udplite_getfrag(void *from, char *to, int  offset,
21 				      int len, int odd, struct sk_buff *skb)
22 {
23 	struct msghdr *msg = from;
24 	return copy_from_iter_full(to, len, &msg->msg_iter) ? 0 : -EFAULT;
25 }
26 
27 /* Designate sk as UDP-Lite socket */
udplite_sk_init(struct sock * sk)28 static inline int udplite_sk_init(struct sock *sk)
29 {
30 	udp_init_sock(sk);
31 	udp_sk(sk)->pcflag = UDPLITE_BIT;
32 	return 0;
33 }
34 
35 /*
36  * 	Checksumming routines
37  */
udplite_checksum_init(struct sk_buff * skb,struct udphdr * uh)38 static inline int udplite_checksum_init(struct sk_buff *skb, struct udphdr *uh)
39 {
40 	u16 cscov;
41 
42         /* In UDPv4 a zero checksum means that the transmitter generated no
43          * checksum. UDP-Lite (like IPv6) mandates checksums, hence packets
44          * with a zero checksum field are illegal.                            */
45 	if (uh->check == 0) {
46 		net_dbg_ratelimited("UDPLite: zeroed checksum field\n");
47 		return 1;
48 	}
49 
50 	cscov = ntohs(uh->len);
51 
52 	if (cscov == 0)		 /* Indicates that full coverage is required. */
53 		;
54 	else if (cscov < 8  || cscov > skb->len) {
55 		/*
56 		 * Coverage length violates RFC 3828: log and discard silently.
57 		 */
58 		net_dbg_ratelimited("UDPLite: bad csum coverage %d/%d\n",
59 				    cscov, skb->len);
60 		return 1;
61 
62 	} else if (cscov < skb->len) {
63         	UDP_SKB_CB(skb)->partial_cov = 1;
64 		UDP_SKB_CB(skb)->cscov = cscov;
65 		if (skb->ip_summed == CHECKSUM_COMPLETE)
66 			skb->ip_summed = CHECKSUM_NONE;
67 		skb->csum_valid = 0;
68         }
69 
70 	return 0;
71 }
72 
73 /* Slow-path computation of checksum. Socket is locked. */
udplite_csum_outgoing(struct sock * sk,struct sk_buff * skb)74 static inline __wsum udplite_csum_outgoing(struct sock *sk, struct sk_buff *skb)
75 {
76 	const struct udp_sock *up = udp_sk(skb->sk);
77 	int cscov = up->len;
78 	__wsum csum = 0;
79 
80 	if (up->pcflag & UDPLITE_SEND_CC) {
81 		/*
82 		 * Sender has set `partial coverage' option on UDP-Lite socket.
83 		 * The special case "up->pcslen == 0" signifies full coverage.
84 		 */
85 		if (up->pcslen < up->len) {
86 			if (0 < up->pcslen)
87 				cscov = up->pcslen;
88 			udp_hdr(skb)->len = htons(up->pcslen);
89 		}
90 		/*
91 		 * NOTE: Causes for the error case  `up->pcslen > up->len':
92 		 *        (i)  Application error (will not be penalized).
93 		 *       (ii)  Payload too big for send buffer: data is split
94 		 *             into several packets, each with its own header.
95 		 *             In this case (e.g. last segment), coverage may
96 		 *             exceed packet length.
97 		 *       Since packets with coverage length > packet length are
98 		 *       illegal, we fall back to the defaults here.
99 		 */
100 	}
101 
102 	skb->ip_summed = CHECKSUM_NONE;     /* no HW support for checksumming */
103 
104 	skb_queue_walk(&sk->sk_write_queue, skb) {
105 		const int off = skb_transport_offset(skb);
106 		const int len = skb->len - off;
107 
108 		csum = skb_checksum(skb, off, (cscov > len)? len : cscov, csum);
109 
110 		if ((cscov -= len) <= 0)
111 			break;
112 	}
113 	return csum;
114 }
115 
116 /* Fast-path computation of checksum. Socket may not be locked. */
udplite_csum(struct sk_buff * skb)117 static inline __wsum udplite_csum(struct sk_buff *skb)
118 {
119 	const struct udp_sock *up = udp_sk(skb->sk);
120 	const int off = skb_transport_offset(skb);
121 	int len = skb->len - off;
122 
123 	if ((up->pcflag & UDPLITE_SEND_CC) && up->pcslen < len) {
124 		if (0 < up->pcslen)
125 			len = up->pcslen;
126 		udp_hdr(skb)->len = htons(up->pcslen);
127 	}
128 	skb->ip_summed = CHECKSUM_NONE;     /* no HW support for checksumming */
129 
130 	return skb_checksum(skb, off, len, 0);
131 }
132 
133 void udplite4_register(void);
134 int udplite_get_port(struct sock *sk, unsigned short snum,
135 		     int (*scmp)(const struct sock *, const struct sock *));
136 #endif	/* _UDPLITE_H */
137