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Linux/include/net/udplite.h

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  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  */
 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 */
 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  */
 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. */
 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. */
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 

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