From c8b17be0b7a45d707fc202c11d257c25bc3952b8 Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Wed, 29 May 2019 13:25:31 +0200 Subject: net: ipv4: add skbuff fraglist splitter This patch adds the skbuff fraglist splitter. This API provides an iterator to transform the fraglist into single skbuff objects, it consists of: * ip_fraglist_init(), that initializes the internal state of the fraglist splitter. * ip_fraglist_prepare(), that restores the IPv4 header on the fragments. * ip_fraglist_next(), that retrieves the fragment from the fraglist and it updates the internal state of the splitter to point to the next fragment skbuff in the fraglist. The ip_fraglist_iter object stores the internal state of the iterator. This code has been extracted from ip_do_fragment(). Symbols are also exported to allow to reuse this iterator from the bridge codepath to build its own refragmentation routine by reusing the existing codebase. Signed-off-by: Pablo Neira Ayuso Signed-off-by: David S. Miller --- net/ipv4/ip_output.c | 88 ++++++++++++++++++++++++++++++++-------------------- 1 file changed, 55 insertions(+), 33 deletions(-) (limited to 'net') diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index bfd0ca554977..d03eb4ae0dd4 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -561,6 +561,54 @@ static int ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, return ip_do_fragment(net, sk, skb, output); } +void ip_fraglist_init(struct sk_buff *skb, struct iphdr *iph, + unsigned int hlen, struct ip_fraglist_iter *iter) +{ + unsigned int first_len = skb_pagelen(skb); + + iter->frag_list = skb_shinfo(skb)->frag_list; + iter->frag = iter->frag_list; + skb_frag_list_init(skb); + + iter->offset = 0; + iter->iph = iph; + iter->hlen = hlen; + + skb->data_len = first_len - skb_headlen(skb); + skb->len = first_len; + iph->tot_len = htons(first_len); + iph->frag_off = htons(IP_MF); + ip_send_check(iph); +} +EXPORT_SYMBOL(ip_fraglist_init); + +void ip_fraglist_prepare(struct sk_buff *skb, struct ip_fraglist_iter *iter) +{ + unsigned int hlen = iter->hlen; + struct iphdr *iph = iter->iph; + struct sk_buff *frag; + + frag = iter->frag; + frag->ip_summed = CHECKSUM_NONE; + skb_reset_transport_header(frag); + __skb_push(frag, hlen); + skb_reset_network_header(frag); + memcpy(skb_network_header(frag), iph, hlen); + iter->iph = ip_hdr(frag); + iph = iter->iph; + iph->tot_len = htons(frag->len); + ip_copy_metadata(frag, skb); + if (iter->offset == 0) + ip_options_fragment(frag); + iter->offset += skb->len - hlen; + iph->frag_off = htons(iter->offset >> 3); + if (frag->next) + iph->frag_off |= htons(IP_MF); + /* Ready, complete checksum */ + ip_send_check(iph); +} +EXPORT_SYMBOL(ip_fraglist_prepare); + /* * This IP datagram is too large to be sent in one piece. Break it up into * smaller pieces (each of size equal to IP header plus @@ -578,6 +626,7 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, int offset; __be16 not_last_frag; struct rtable *rt = skb_rtable(skb); + struct ip_fraglist_iter iter; int err = 0; /* for offloaded checksums cleanup checksum before fragmentation */ @@ -642,49 +691,22 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, } /* Everything is OK. Generate! */ - - err = 0; - offset = 0; - frag = skb_shinfo(skb)->frag_list; - skb_frag_list_init(skb); - skb->data_len = first_len - skb_headlen(skb); - skb->len = first_len; - iph->tot_len = htons(first_len); - iph->frag_off = htons(IP_MF); - ip_send_check(iph); + ip_fraglist_init(skb, iph, hlen, &iter); for (;;) { /* Prepare header of the next frame, * before previous one went down. */ - if (frag) { - frag->ip_summed = CHECKSUM_NONE; - skb_reset_transport_header(frag); - __skb_push(frag, hlen); - skb_reset_network_header(frag); - memcpy(skb_network_header(frag), iph, hlen); - iph = ip_hdr(frag); - iph->tot_len = htons(frag->len); - ip_copy_metadata(frag, skb); - if (offset == 0) - ip_options_fragment(frag); - offset += skb->len - hlen; - iph->frag_off = htons(offset>>3); - if (frag->next) - iph->frag_off |= htons(IP_MF); - /* Ready, complete checksum */ - ip_send_check(iph); - } + if (iter.frag) + ip_fraglist_prepare(skb, &iter); err = output(net, sk, skb); if (!err) IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES); - if (err || !frag) + if (err || !iter.frag) break; - skb = frag; - frag = skb->next; - skb_mark_not_on_list(skb); + skb = ip_fraglist_next(&iter); } if (err == 0) { @@ -692,7 +714,7 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, return 0; } - kfree_skb_list(frag); + kfree_skb_list(iter.frag_list); IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS); return err; -- cgit v1.2.3