root/include/net/udplite.h

INCLUDED FROM

DEFINITIONS

1. udplite_getfrag
2. udplite_sk_init
3. udplite_checksum_init
4. udplite_sender_cscov
5. udplite_csum_outgoing

/*
 *      Definitions for the UDP-Lite (RFC 3828) code.
 */
#ifndef _UDPLITE_H
#define _UDPLITE_H

#include <net/ip6_checksum.h>

/* UDP-Lite socket options */
#define UDPLITE_SEND_CSCOV   10 /* sender partial coverage (as sent)      */
#define UDPLITE_RECV_CSCOV   11 /* receiver partial coverage (threshold ) */

extern struct proto             udplite_prot;
extern struct hlist_head        udplite_hash[UDP_HTABLE_SIZE];

/*
 *      Checksum computation is all in software, hence simpler getfrag.
 */
static __inline__ int udplite_getfrag(void *from, char *to, int  offset,
                                      int len, int odd, struct sk_buff *skb)
{
        return memcpy_fromiovecend(to, (struct iovec *) from, offset, len);
}

/* Designate sk as UDP-Lite socket */
static inline int udplite_sk_init(struct sock *sk)
{
        udp_sk(sk)->pcflag = UDPLITE_BIT;
        return 0;
}

/*
 *      Checksumming routines
 */
static inline int udplite_checksum_init(struct sk_buff *skb, struct udphdr *uh)
{
        u16 cscov;

        /* In UDPv4 a zero checksum means that the transmitter generated no
         * checksum. UDP-Lite (like IPv6) mandates checksums, hence packets
         * with a zero checksum field are illegal.                            */
        if (uh->check == 0) {
                LIMIT_NETDEBUG(KERN_DEBUG "UDPLITE: zeroed checksum field\n");
                return 1;
        }

        cscov = ntohs(uh->len);

        if (cscov == 0)          /* Indicates that full coverage is required. */
                ;
        else if (cscov < 8  || cscov > skb->len) {
                /*
                 * Coverage length violates RFC 3828: log and discard silently.
                 */
                LIMIT_NETDEBUG(KERN_DEBUG "UDPLITE: bad csum coverage %d/%d\n",
                               cscov, skb->len);
                return 1;

        } else if (cscov < skb->len) {
                UDP_SKB_CB(skb)->partial_cov = 1;
                UDP_SKB_CB(skb)->cscov = cscov;
                if (skb->ip_summed == CHECKSUM_COMPLETE)
                        skb->ip_summed = CHECKSUM_NONE;
        }

        return 0;
}

static inline int udplite_sender_cscov(struct udp_sock *up, struct udphdr *uh)
{
        int cscov = up->len;

        /*
         * Sender has set `partial coverage' option on UDP-Lite socket
         */
        if (up->pcflag & UDPLITE_SEND_CC)    {
                if (up->pcslen < up->len) {
                /* up->pcslen == 0 means that full coverage is required,
                 * partial coverage only if  0 < up->pcslen < up->len */
                        if (0 < up->pcslen) {
                               cscov = up->pcslen;
                        }
                        uh->len = htons(up->pcslen);
                }
        /*
         * NOTE: Causes for the error case  `up->pcslen > up->len':
         *        (i)  Application error (will not be penalized).
         *       (ii)  Payload too big for send buffer: data is split
         *             into several packets, each with its own header.
         *             In this case (e.g. last segment), coverage may
         *             exceed packet length.
         *       Since packets with coverage length > packet length are
         *       illegal, we fall back to the defaults here.
         */
        }
        return cscov;
}

static inline __wsum udplite_csum_outgoing(struct sock *sk, struct sk_buff *skb)
{
        int cscov = udplite_sender_cscov(udp_sk(sk), udp_hdr(skb));
        __wsum csum = 0;

        skb->ip_summed = CHECKSUM_NONE;     /* no HW support for checksumming */

        skb_queue_walk(&sk->sk_write_queue, skb) {
                const int off = skb_transport_offset(skb);
                const int len = skb->len - off;

                csum = skb_checksum(skb, off, (cscov > len)? len : cscov, csum);

                if ((cscov -= len) <= 0)
                        break;
        }
        return csum;
}

extern void     udplite4_register(void);
extern int      udplite_get_port(struct sock *sk, unsigned short snum,
                        int (*scmp)(const struct sock *, const struct sock *));
#endif  /* _UDPLITE_H */