LXR linux/include/net/udplite.h

   1/* SPDX-License-Identifier: GPL-2.0 */
   2/*
   3 *      Definitions for the UDP-Lite (RFC 3828) code.
   4 */
   5#ifndef _UDPLITE_H
   6#define _UDPLITE_H
   7
   8#include <net/ip6_checksum.h>
   9
  10/* UDP-Lite socket options */
  11#define UDPLITE_SEND_CSCOV   10 /* sender partial coverage (as sent)      */
  12#define UDPLITE_RECV_CSCOV   11 /* receiver partial coverage (threshold ) */
  13
  14extern struct proto             udplite_prot;
  15extern struct udp_table         udplite_table;
  16
  17/*
  18 *      Checksum computation is all in software, hence simpler getfrag.
  19 */
  20static __inline__ int udplite_getfrag(void *from, char *to, int  offset,
  21                                      int len, int odd, struct sk_buff *skb)
  22{
  23        struct msghdr *msg = from;
  24        return copy_from_iter_full(to, len, &msg->msg_iter) ? 0 : -EFAULT;
  25}
  26
  27/* Designate sk as UDP-Lite socket */
  28static inline int udplite_sk_init(struct sock *sk)
  29{
  30        udp_init_sock(sk);
  31        udp_sk(sk)->pcflag = UDPLITE_BIT;
  32        return 0;
  33}
  34
  35/*
  36 *      Checksumming routines
  37 */
  38static 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                net_dbg_ratelimited("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                net_dbg_ratelimited("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                skb->csum_valid = 0;
  68        }
  69
  70        return 0;
  71}
  72
  73/* Slow-path computation of checksum. Socket is locked. */
  74static inline __wsum udplite_csum_outgoing(struct sock *sk, struct sk_buff *skb)
  75{
  76        const struct udp_sock *up = udp_sk(skb->sk);
  77        int cscov = up->len;
  78        __wsum csum = 0;
  79
  80        if (up->pcflag & UDPLITE_SEND_CC) {
  81                /*
  82                 * Sender has set `partial coverage' option on UDP-Lite socket.
  83                 * The special case "up->pcslen == 0" signifies full coverage.
  84                 */
  85                if (up->pcslen < up->len) {
  86                        if (0 < up->pcslen)
  87                                cscov = up->pcslen;
  88                        udp_hdr(skb)->len = htons(up->pcslen);
  89                }
  90                /*
  91                 * NOTE: Causes for the error case  `up->pcslen > up->len':
  92                 *        (i)  Application error (will not be penalized).
  93                 *       (ii)  Payload too big for send buffer: data is split
  94                 *             into several packets, each with its own header.
  95                 *             In this case (e.g. last segment), coverage may
  96                 *             exceed packet length.
  97                 *       Since packets with coverage length > packet length are
  98                 *       illegal, we fall back to the defaults here.
  99                 */
 100        }
 101
 102        skb->ip_summed = CHECKSUM_NONE;     /* no HW support for checksumming */
 103
 104        skb_queue_walk(&sk->sk_write_queue, skb) {
 105                const int off = skb_transport_offset(skb);
 106                const int len = skb->len - off;
 107
 108                csum = skb_checksum(skb, off, (cscov > len)? len : cscov, csum);
 109
 110                if ((cscov -= len) <= 0)
 111                        break;
 112        }
 113        return csum;
 114}
 115
 116/* Fast-path computation of checksum. Socket may not be locked. */
 117static inline __wsum udplite_csum(struct sk_buff *skb)
 118{
 119        const struct udp_sock *up = udp_sk(skb->sk);
 120        const int off = skb_transport_offset(skb);
 121        int len = skb->len - off;
 122
 123        if ((up->pcflag & UDPLITE_SEND_CC) && up->pcslen < len) {
 124                if (0 < up->pcslen)
 125                        len = up->pcslen;
 126                udp_hdr(skb)->len = htons(up->pcslen);
 127        }
 128        skb->ip_summed = CHECKSUM_NONE;     /* no HW support for checksumming */
 129
 130        return skb_checksum(skb, off, len, 0);
 131}
 132
 133void udplite4_register(void);
 134int udplite_get_port(struct sock *sk, unsigned short snum,
 135                     int (*scmp)(const struct sock *, const struct sock *));
 136#endif  /* _UDPLITE_H */
 137