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TOMOYO Linux Cross Reference
Linux/include/net/udplite.h

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  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 */
134 

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