LXR linux/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
  13extern struct proto             udplite_prot;
  14extern struct udp_table         udplite_table;
  15
  16/*
  17 *      Checksum computation is all in software, hence simpler getfrag.
  18 */
  19static __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 */
  26static 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 */
  35static 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. */
  70static 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. */
 113static 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
 129extern void     udplite4_register(void);
 130extern int      udplite_get_port(struct sock *sk, unsigned short snum,
 131                        int (*scmp)(const struct sock *, const struct sock *));
 132#endif  /* _UDPLITE_H */
 133