include/net/udplite.h

   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 */