xref: /linux/include/net/udplite.h (revision 827634added7f38b7d724cab1dccdb2b004c13c3)
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 
13 extern struct proto 		udplite_prot;
14 extern struct udp_table		udplite_table;
15 
16 /*
17  *	Checksum computation is all in software, hence simpler getfrag.
18  */
19 static __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 */
27 static 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  */
36 static 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. */
71 static 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. */
114 static 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 
130 void udplite4_register(void);
131 int udplite_get_port(struct sock *sk, unsigned short snum,
132 		     int (*scmp)(const struct sock *, const struct sock *));
133 #endif	/* _UDPLITE_H */
134