diff options
Diffstat (limited to 'net/core/skbuff.c')
| -rw-r--r-- | net/core/skbuff.c | 188 |
1 files changed, 188 insertions, 0 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 331d3efa82fa..f927b6e8027e 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -55,6 +55,7 @@ #include <linux/cache.h> #include <linux/rtnetlink.h> #include <linux/init.h> +#include <linux/scatterlist.h> #include <net/protocol.h> #include <net/dst.h> @@ -2002,6 +2003,190 @@ void __init skb_init(void) NULL, NULL); } +/** + * skb_to_sgvec - Fill a scatter-gather list from a socket buffer + * @skb: Socket buffer containing the buffers to be mapped + * @sg: The scatter-gather list to map into + * @offset: The offset into the buffer's contents to start mapping + * @len: Length of buffer space to be mapped + * + * Fill the specified scatter-gather list with mappings/pointers into a + * region of the buffer space attached to a socket buffer. + */ +int +skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len) +{ + int start = skb_headlen(skb); + int i, copy = start - offset; + int elt = 0; + + if (copy > 0) { + if (copy > len) + copy = len; + sg[elt].page = virt_to_page(skb->data + offset); + sg[elt].offset = (unsigned long)(skb->data + offset) % PAGE_SIZE; + sg[elt].length = copy; + elt++; + if ((len -= copy) == 0) + return elt; + offset += copy; + } + + for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) { + int end; + + BUG_TRAP(start <= offset + len); + + end = start + skb_shinfo(skb)->frags[i].size; + if ((copy = end - offset) > 0) { + skb_frag_t *frag = &skb_shinfo(skb)->frags[i]; + + if (copy > len) + copy = len; + sg[elt].page = frag->page; + sg[elt].offset = frag->page_offset+offset-start; + sg[elt].length = copy; + elt++; + if (!(len -= copy)) + return elt; + offset += copy; + } + start = end; + } + + if (skb_shinfo(skb)->frag_list) { + struct sk_buff *list = skb_shinfo(skb)->frag_list; + + for (; list; list = list->next) { + int end; + + BUG_TRAP(start <= offset + len); + + end = start + list->len; + if ((copy = end - offset) > 0) { + if (copy > len) + copy = len; + elt += skb_to_sgvec(list, sg+elt, offset - start, copy); + if ((len -= copy) == 0) + return elt; + offset += copy; + } + start = end; + } + } + BUG_ON(len); + return elt; +} + +/** + * skb_cow_data - Check that a socket buffer's data buffers are writable + * @skb: The socket buffer to check. + * @tailbits: Amount of trailing space to be added + * @trailer: Returned pointer to the skb where the @tailbits space begins + * + * Make sure that the data buffers attached to a socket buffer are + * writable. If they are not, private copies are made of the data buffers + * and the socket buffer is set to use these instead. + * + * If @tailbits is given, make sure that there is space to write @tailbits + * bytes of data beyond current end of socket buffer. @trailer will be + * set to point to the skb in which this space begins. + * + * The number of scatterlist elements required to completely map the + * COW'd and extended socket buffer will be returned. + */ +int skb_cow_data(struct sk_buff *skb, int tailbits, struct sk_buff **trailer) +{ + int copyflag; + int elt; + struct sk_buff *skb1, **skb_p; + + /* If skb is cloned or its head is paged, reallocate + * head pulling out all the pages (pages are considered not writable + * at the moment even if they are anonymous). + */ + if ((skb_cloned(skb) || skb_shinfo(skb)->nr_frags) && + __pskb_pull_tail(skb, skb_pagelen(skb)-skb_headlen(skb)) == NULL) + return -ENOMEM; + + /* Easy case. Most of packets will go this way. */ + if (!skb_shinfo(skb)->frag_list) { + /* A little of trouble, not enough of space for trailer. + * This should not happen, when stack is tuned to generate + * good frames. OK, on miss we reallocate and reserve even more + * space, 128 bytes is fair. */ + + if (skb_tailroom(skb) < tailbits && + pskb_expand_head(skb, 0, tailbits-skb_tailroom(skb)+128, GFP_ATOMIC)) + return -ENOMEM; + + /* Voila! */ + *trailer = skb; + return 1; + } + + /* Misery. We are in troubles, going to mincer fragments... */ + + elt = 1; + skb_p = &skb_shinfo(skb)->frag_list; + copyflag = 0; + + while ((skb1 = *skb_p) != NULL) { + int ntail = 0; + + /* The fragment is partially pulled by someone, + * this can happen on input. Copy it and everything + * after it. */ + + if (skb_shared(skb1)) + copyflag = 1; + + /* If the skb is the last, worry about trailer. */ + + if (skb1->next == NULL && tailbits) { + if (skb_shinfo(skb1)->nr_frags || + skb_shinfo(skb1)->frag_list || + skb_tailroom(skb1) < tailbits) + ntail = tailbits + 128; + } + + if (copyflag || + skb_cloned(skb1) || + ntail || + skb_shinfo(skb1)->nr_frags || + skb_shinfo(skb1)->frag_list) { + struct sk_buff *skb2; + + /* Fuck, we are miserable poor guys... */ + if (ntail == 0) + skb2 = skb_copy(skb1, GFP_ATOMIC); + else + skb2 = skb_copy_expand(skb1, + skb_headroom(skb1), + ntail, + GFP_ATOMIC); + if (unlikely(skb2 == NULL)) + return -ENOMEM; + + if (skb1->sk) + skb_set_owner_w(skb2, skb1->sk); + + /* Looking around. Are we still alive? + * OK, link new skb, drop old one */ + + skb2->next = skb1->next; + *skb_p = skb2; + kfree_skb(skb1); + skb1 = skb2; + } + elt++; + *trailer = skb1; + skb_p = &skb1->next; + } + + return elt; +} + EXPORT_SYMBOL(___pskb_trim); EXPORT_SYMBOL(__kfree_skb); EXPORT_SYMBOL(kfree_skb); @@ -2036,3 +2221,6 @@ EXPORT_SYMBOL(skb_seq_read); EXPORT_SYMBOL(skb_abort_seq_read); EXPORT_SYMBOL(skb_find_text); EXPORT_SYMBOL(skb_append_datato_frags); + +EXPORT_SYMBOL_GPL(skb_to_sgvec); +EXPORT_SYMBOL_GPL(skb_cow_data); |