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 hlist_head        udplite_hash[UDP_HTABLE_SIZE];
  15
  16 /* UDP-Lite does not have a standardized MIB yet, so we inherit from UDP */
  17 DECLARE_SNMP_STAT(struct udp_mib, udplite_statistics);
  18
  19 /*
  20  *      Checksum computation is all in software, hence simpler getfrag.
  21  */
  22 static __inline__ int udplite_getfrag(void *from, char *to, int  offset,
  23                                       int len, int odd, struct sk_buff *skb)
  24 {
  25         return memcpy_fromiovecend(to, (struct iovec *) from, offset, len);
  26 }
  27
  28 /* Designate sk as UDP-Lite socket */
  29 static inline int udplite_sk_init(struct sock *sk)
  30 {
  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                 LIMIT_NETDEBUG(KERN_DEBUG "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                 LIMIT_NETDEBUG(KERN_DEBUG "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         }
  68
  69         return 0;
  70 }
  71
  72 static inline int udplite_sender_cscov(struct udp_sock *up, struct udphdr *uh)
  73 {
  74         int cscov = up->len;
  75
  76         /*
  77          * Sender has set `partial coverage' option on UDP-Lite socket
  78          */
  79         if (up->pcflag & UDPLITE_SEND_CC)    {
  80                 if (up->pcslen < up->len) {
  81                 /* up->pcslen == 0 means that full coverage is required,
  82                  * partial coverage only if  0 < up->pcslen < up->len */
  83                         if (0 < up->pcslen) {
  84                                cscov = up->pcslen;
  85                         }
  86                         uh->len = htons(up->pcslen);
  87                 }
  88         /*
  89          * NOTE: Causes for the error case  `up->pcslen > up->len':
  90          *        (i)  Application error (will not be penalized).
  91          *       (ii)  Payload too big for send buffer: data is split
  92          *             into several packets, each with its own header.
  93          *             In this case (e.g. last segment), coverage may
  94          *             exceed packet length.
  95          *       Since packets with coverage length > packet length are
  96          *       illegal, we fall back to the defaults here.
  97          */
  98         }
  99         return cscov;
 100 }
 101
 102 static inline __wsum udplite_csum_outgoing(struct sock *sk, struct sk_buff *skb)
 103 {
 104         int cscov = udplite_sender_cscov(udp_sk(sk), udp_hdr(skb));
 105         __wsum csum = 0;
 106
 107         skb->ip_summed = CHECKSUM_NONE;     /* no HW support for checksumming */
 108
 109         skb_queue_walk(&sk->sk_write_queue, skb) {
 110                 const int off = skb_transport_offset(skb);
 111                 const int len = skb->len - off;
 112
 113                 csum = skb_checksum(skb, off, (cscov > len)? len : cscov, csum);
 114
 115                 if ((cscov -= len) <= 0)
 116                         break;
 117         }
 118         return csum;
 119 }
 120
 121 extern void     udplite4_register(void);
 122 extern int      udplite_get_port(struct sock *sk, unsigned short snum,
 123                         int (*scmp)(const struct sock *, const struct sock *));
 124 #endif  /* _UDPLITE_H */