include/net/udplite.h

   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 */