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