net/sunrpc/socklib.c

   1 /*
   2  * linux/net/sunrpc/socklib.c
   3  *
   4  * Common socket helper routines for RPC client and server
   5  *
   6  * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
   7  */
   8
   9 #include <linux/compiler.h>
  10 #include <linux/netdevice.h>
  11 #include <linux/skbuff.h>
  12 #include <linux/types.h>
  13 #include <linux/pagemap.h>
  14 #include <linux/udp.h>
  15 #include <linux/sunrpc/xdr.h>
  16
  17
  18 /**
  19  * skb_read_bits - copy some data bits from skb to internal buffer
  20  * @desc: sk_buff copy helper
  21  * @to: copy destination
  22  * @len: number of bytes to copy
  23  *
  24  * Possibly called several times to iterate over an sk_buff and copy
  25  * data out of it.
  26  */
  27 static size_t skb_read_bits(skb_reader_t *desc, void *to, size_t len)
  28 {
  29         if (len > desc->count)
  30                 len = desc->count;
  31         if (skb_copy_bits(desc->skb, desc->offset, to, len))
  32                 return 0;
  33         desc->count -= len;
  34         desc->offset += len;
  35         return len;
  36 }
  37
  38 /**
  39  * skb_read_and_csum_bits - copy and checksum from skb to buffer
  40  * @desc: sk_buff copy helper
  41  * @to: copy destination
  42  * @len: number of bytes to copy
  43  *
  44  * Same as skb_read_bits, but calculate a checksum at the same time.
  45  */
  46 static size_t skb_read_and_csum_bits(skb_reader_t *desc, void *to, size_t len)
  47 {
  48         unsigned int    csum2, pos;
  49
  50         if (len > desc->count)
  51                 len = desc->count;
  52         pos = desc->offset;
  53         csum2 = skb_copy_and_csum_bits(desc->skb, pos, to, len, 0);
  54         desc->csum = csum_block_add(desc->csum, csum2, pos);
  55         desc->count -= len;
  56         desc->offset += len;
  57         return len;
  58 }
  59
  60 /**
  61  * xdr_partial_copy_from_skb - copy data out of an skb
  62  * @xdr: target XDR buffer
  63  * @base: starting offset
  64  * @desc: sk_buff copy helper
  65  * @copy_actor: virtual method for copying data
  66  *
  67  */
  68 ssize_t xdr_partial_copy_from_skb(struct xdr_buf *xdr, unsigned int base, skb_reader_t *desc, skb_read_actor_t copy_actor)
  69 {
  70         struct page     **ppage = xdr->pages;
  71         unsigned int    len, pglen = xdr->page_len;
  72         ssize_t         copied = 0;
  73         int             ret;
  74
  75         len = xdr->head[0].iov_len;
  76         if (base < len) {
  77                 len -= base;
  78                 ret = copy_actor(desc, (char *)xdr->head[0].iov_base + base, len);
  79                 copied += ret;
  80                 if (ret != len || !desc->count)
  81                         goto out;
  82                 base = 0;
  83         } else
  84                 base -= len;
  85
  86         if (unlikely(pglen == 0))
  87                 goto copy_tail;
  88         if (unlikely(base >= pglen)) {
  89                 base -= pglen;
  90                 goto copy_tail;
  91         }
  92         if (base || xdr->page_base) {
  93                 pglen -= base;
  94                 base += xdr->page_base;
  95                 ppage += base >> PAGE_CACHE_SHIFT;
  96                 base &= ~PAGE_CACHE_MASK;
  97         }
  98         do {
  99                 char *kaddr;
 100
 101                 /* ACL likes to be lazy in allocating pages - ACLs
 102                  * are small by default but can get huge. */
 103                 if (unlikely(*ppage == NULL)) {
 104                         *ppage = alloc_page(GFP_ATOMIC);
 105                         if (unlikely(*ppage == NULL)) {
 106                                 if (copied == 0)
 107                                         copied = -ENOMEM;
 108                                 goto out;
 109                         }
 110                 }
 111
 112                 len = PAGE_CACHE_SIZE;
 113                 kaddr = kmap_atomic(*ppage, KM_SKB_SUNRPC_DATA);
 114                 if (base) {
 115                         len -= base;
 116                         if (pglen < len)
 117                                 len = pglen;
 118                         ret = copy_actor(desc, kaddr + base, len);
 119                         base = 0;
 120                 } else {
 121                         if (pglen < len)
 122                                 len = pglen;
 123                         ret = copy_actor(desc, kaddr, len);
 124                 }
 125                 flush_dcache_page(*ppage);
 126                 kunmap_atomic(kaddr, KM_SKB_SUNRPC_DATA);
 127                 copied += ret;
 128                 if (ret != len || !desc->count)
 129                         goto out;
 130                 ppage++;
 131         } while ((pglen -= len) != 0);
 132 copy_tail:
 133         len = xdr->tail[0].iov_len;
 134         if (base < len)
 135                 copied += copy_actor(desc, (char *)xdr->tail[0].iov_base + base, len - base);
 136 out:
 137         return copied;
 138 }
 139
 140 /**
 141  * csum_partial_copy_to_xdr - checksum and copy data
 142  * @xdr: target XDR buffer
 143  * @skb: source skb
 144  *
 145  * We have set things up such that we perform the checksum of the UDP
 146  * packet in parallel with the copies into the RPC client iovec.  -DaveM
 147  */
 148 int csum_partial_copy_to_xdr(struct xdr_buf *xdr, struct sk_buff *skb)
 149 {
 150         skb_reader_t    desc;
 151
 152         desc.skb = skb;
 153         desc.offset = sizeof(struct udphdr);
 154         desc.count = skb->len - desc.offset;
 155
 156         if (skb->ip_summed == CHECKSUM_UNNECESSARY)
 157                 goto no_checksum;
 158
 159         desc.csum = csum_partial(skb->data, desc.offset, skb->csum);
 160         if (xdr_partial_copy_from_skb(xdr, 0, &desc, skb_read_and_csum_bits) < 0)
 161                 return -1;
 162         if (desc.offset != skb->len) {
 163                 unsigned int csum2;
 164                 csum2 = skb_checksum(skb, desc.offset, skb->len - desc.offset, 0);
 165                 desc.csum = csum_block_add(desc.csum, csum2, desc.offset);
 166         }
 167         if (desc.count)
 168                 return -1;
 169         if ((unsigned short)csum_fold(desc.csum))
 170                 return -1;
 171         if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
 172                 netdev_rx_csum_fault(skb->dev);
 173         return 0;
 174 no_checksum:
 175         if (xdr_partial_copy_from_skb(xdr, 0, &desc, skb_read_bits) < 0)
 176                 return -1;
 177         if (desc.count)
 178                 return -1;
 179         return 0;
 180 }