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net: IP6 defrag: use rbtrees in nf_conntrack_reasm.c
Currently, IPv6 defragmentation code drops non-last fragments that
are smaller than 1280 bytes: see
commit 0ed4229b08 ("ipv6: defrag: drop non-last frags smaller than min mtu")
This behavior is not specified in IPv6 RFCs and appears to break
compatibility with some IPv6 implemenations, as reported here:
https://www.spinics.net/lists/netdev/msg543846.html
This patch re-uses common IP defragmentation queueing and reassembly
code in IP6 defragmentation in nf_conntrack, removing the 1280 byte
restriction.
Signed-off-by: Peter Oskolkov <posk@google.com>
Reported-by: Tom Herbert <tom@herbertland.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Peter Oskolkov
David S. Miller
parent
d4289fcc9b
commit
997dd96471
@ -136,6 +136,9 @@ static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
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}
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#endif
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static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb,
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struct sk_buff *prev_tail, struct net_device *dev);
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static inline u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h)
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{
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return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK);
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@ -177,9 +180,10 @@ static struct frag_queue *fq_find(struct net *net, __be32 id, u32 user,
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static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb,
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const struct frag_hdr *fhdr, int nhoff)
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{
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struct sk_buff *prev, *next;
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unsigned int payload_len;
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int offset, end;
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struct net_device *dev;
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struct sk_buff *prev;
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int offset, end, err;
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u8 ecn;
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if (fq->q.flags & INET_FRAG_COMPLETE) {
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@ -254,55 +258,18 @@ static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb,
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goto err;
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}
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/* Find out which fragments are in front and at the back of us
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* in the chain of fragments so far. We must know where to put
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* this fragment, right?
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*/
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prev = fq->q.fragments_tail;
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if (!prev || prev->ip_defrag_offset < offset) {
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next = NULL;
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goto found;
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}
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prev = NULL;
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for (next = fq->q.fragments; next != NULL; next = next->next) {
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if (next->ip_defrag_offset >= offset)
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break; /* bingo! */
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prev = next;
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}
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found:
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/* RFC5722, Section 4:
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* When reassembling an IPv6 datagram, if
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* one or more its constituent fragments is determined to be an
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* overlapping fragment, the entire datagram (and any constituent
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* fragments, including those not yet received) MUST be silently
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* discarded.
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*/
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/* Check for overlap with preceding fragment. */
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if (prev &&
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(prev->ip_defrag_offset + prev->len) > offset)
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goto discard_fq;
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/* Look for overlap with succeeding segment. */
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if (next && next->ip_defrag_offset < end)
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goto discard_fq;
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/* Note : skb->ip_defrag_offset and skb->dev share the same location */
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if (skb->dev)
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fq->iif = skb->dev->ifindex;
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/* Note : skb->rbnode and skb->dev share the same location. */
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dev = skb->dev;
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/* Makes sure compiler wont do silly aliasing games */
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barrier();
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skb->ip_defrag_offset = offset;
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/* Insert this fragment in the chain of fragments. */
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skb->next = next;
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if (!next)
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fq->q.fragments_tail = skb;
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if (prev)
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prev->next = skb;
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else
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fq->q.fragments = skb;
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prev = fq->q.fragments_tail;
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err = inet_frag_queue_insert(&fq->q, skb, offset, end);
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if (err)
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goto insert_error;
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if (dev)
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fq->iif = dev->ifindex;
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fq->q.stamp = skb->tstamp;
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fq->q.meat += skb->len;
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@ -319,11 +286,25 @@ found:
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fq->q.flags |= INET_FRAG_FIRST_IN;
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}
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return 0;
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if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
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fq->q.meat == fq->q.len) {
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unsigned long orefdst = skb->_skb_refdst;
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discard_fq:
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skb->_skb_refdst = 0UL;
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err = nf_ct_frag6_reasm(fq, skb, prev, dev);
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skb->_skb_refdst = orefdst;
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return err;
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}
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skb_dst_drop(skb);
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return -EINPROGRESS;
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insert_error:
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if (err == IPFRAG_DUP)
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goto err;
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inet_frag_kill(&fq->q);
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err:
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skb_dst_drop(skb);
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return -EINVAL;
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}
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@ -333,147 +314,67 @@ err:
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* It is called with locked fq, and caller must check that
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* queue is eligible for reassembly i.e. it is not COMPLETE,
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* the last and the first frames arrived and all the bits are here.
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*
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* returns true if *prev skb has been transformed into the reassembled
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* skb, false otherwise.
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*/
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static bool
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nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *prev, struct net_device *dev)
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static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb,
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struct sk_buff *prev_tail, struct net_device *dev)
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{
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struct sk_buff *fp, *head = fq->q.fragments;
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int payload_len, delta;
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void *reasm_data;
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int payload_len;
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u8 ecn;
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inet_frag_kill(&fq->q);
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WARN_ON(head == NULL);
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WARN_ON(head->ip_defrag_offset != 0);
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ecn = ip_frag_ecn_table[fq->ecn];
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if (unlikely(ecn == 0xff))
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return false;
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goto err;
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/* Unfragmented part is taken from the first segment. */
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payload_len = ((head->data - skb_network_header(head)) -
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reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
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if (!reasm_data)
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goto err;
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payload_len = ((skb->data - skb_network_header(skb)) -
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sizeof(struct ipv6hdr) + fq->q.len -
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sizeof(struct frag_hdr));
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if (payload_len > IPV6_MAXPLEN) {
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net_dbg_ratelimited("nf_ct_frag6_reasm: payload len = %d\n",
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payload_len);
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return false;
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}
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delta = - head->truesize;
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/* Head of list must not be cloned. */
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if (skb_unclone(head, GFP_ATOMIC))
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return false;
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delta += head->truesize;
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if (delta)
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add_frag_mem_limit(fq->q.net, delta);
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/* If the first fragment is fragmented itself, we split
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* it to two chunks: the first with data and paged part
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* and the second, holding only fragments. */
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if (skb_has_frag_list(head)) {
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struct sk_buff *clone;
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int i, plen = 0;
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clone = alloc_skb(0, GFP_ATOMIC);
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if (clone == NULL)
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return false;
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clone->next = head->next;
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head->next = clone;
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skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
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skb_frag_list_init(head);
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for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
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plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
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clone->len = clone->data_len = head->data_len - plen;
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head->data_len -= clone->len;
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head->len -= clone->len;
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clone->csum = 0;
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clone->ip_summed = head->ip_summed;
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add_frag_mem_limit(fq->q.net, clone->truesize);
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}
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/* morph head into last received skb: prev.
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*
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* This allows callers of ipv6 conntrack defrag to continue
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* to use the last skb(frag) passed into the reasm engine.
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* The last skb frag 'silently' turns into the full reassembled skb.
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*
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* Since prev is also part of q->fragments we have to clone it first.
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*/
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if (head != prev) {
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struct sk_buff *iter;
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fp = skb_clone(prev, GFP_ATOMIC);
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if (!fp)
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return false;
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fp->next = prev->next;
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iter = head;
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while (iter) {
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if (iter->next == prev) {
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iter->next = fp;
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break;
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}
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iter = iter->next;
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}
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skb_morph(prev, head);
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prev->next = head->next;
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consume_skb(head);
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head = prev;
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goto err;
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}
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/* We have to remove fragment header from datagram and to relocate
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* header in order to calculate ICV correctly. */
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skb_network_header(head)[fq->nhoffset] = skb_transport_header(head)[0];
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memmove(head->head + sizeof(struct frag_hdr), head->head,
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(head->data - head->head) - sizeof(struct frag_hdr));
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head->mac_header += sizeof(struct frag_hdr);
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head->network_header += sizeof(struct frag_hdr);
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skb_network_header(skb)[fq->nhoffset] = skb_transport_header(skb)[0];
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memmove(skb->head + sizeof(struct frag_hdr), skb->head,
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(skb->data - skb->head) - sizeof(struct frag_hdr));
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skb->mac_header += sizeof(struct frag_hdr);
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skb->network_header += sizeof(struct frag_hdr);
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skb_shinfo(head)->frag_list = head->next;
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skb_reset_transport_header(head);
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skb_push(head, head->data - skb_network_header(head));
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skb_reset_transport_header(skb);
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for (fp = head->next; fp; fp = fp->next) {
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head->data_len += fp->len;
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head->len += fp->len;
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if (head->ip_summed != fp->ip_summed)
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head->ip_summed = CHECKSUM_NONE;
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else if (head->ip_summed == CHECKSUM_COMPLETE)
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head->csum = csum_add(head->csum, fp->csum);
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head->truesize += fp->truesize;
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fp->sk = NULL;
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}
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sub_frag_mem_limit(fq->q.net, head->truesize);
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inet_frag_reasm_finish(&fq->q, skb, reasm_data);
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head->ignore_df = 1;
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skb_mark_not_on_list(head);
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head->dev = dev;
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head->tstamp = fq->q.stamp;
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ipv6_hdr(head)->payload_len = htons(payload_len);
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ipv6_change_dsfield(ipv6_hdr(head), 0xff, ecn);
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IP6CB(head)->frag_max_size = sizeof(struct ipv6hdr) + fq->q.max_size;
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skb->ignore_df = 1;
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skb->dev = dev;
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ipv6_hdr(skb)->payload_len = htons(payload_len);
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ipv6_change_dsfield(ipv6_hdr(skb), 0xff, ecn);
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IP6CB(skb)->frag_max_size = sizeof(struct ipv6hdr) + fq->q.max_size;
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/* Yes, and fold redundant checksum back. 8) */
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if (head->ip_summed == CHECKSUM_COMPLETE)
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head->csum = csum_partial(skb_network_header(head),
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skb_network_header_len(head),
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head->csum);
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if (skb->ip_summed == CHECKSUM_COMPLETE)
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skb->csum = csum_partial(skb_network_header(skb),
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skb_network_header_len(skb),
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skb->csum);
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fq->q.fragments = NULL;
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fq->q.rb_fragments = RB_ROOT;
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fq->q.fragments_tail = NULL;
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fq->q.last_run_head = NULL;
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return true;
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return 0;
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err:
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inet_frag_kill(&fq->q);
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return -EINVAL;
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}
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/*
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@ -542,7 +443,6 @@ find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff)
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int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user)
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{
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u16 savethdr = skb->transport_header;
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struct net_device *dev = skb->dev;
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int fhoff, nhoff, ret;
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struct frag_hdr *fhdr;
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struct frag_queue *fq;
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@ -565,10 +465,6 @@ int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user)
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hdr = ipv6_hdr(skb);
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fhdr = (struct frag_hdr *)skb_transport_header(skb);
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if (skb->len - skb_network_offset(skb) < IPV6_MIN_MTU &&
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fhdr->frag_off & htons(IP6_MF))
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return -EINVAL;
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skb_orphan(skb);
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fq = fq_find(net, fhdr->identification, user, hdr,
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skb->dev ? skb->dev->ifindex : 0);
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@ -580,31 +476,17 @@ int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user)
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spin_lock_bh(&fq->q.lock);
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ret = nf_ct_frag6_queue(fq, skb, fhdr, nhoff);
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if (ret < 0) {
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if (ret == -EPROTO) {
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skb->transport_header = savethdr;
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ret = 0;
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}
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goto out_unlock;
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}
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/* after queue has assumed skb ownership, only 0 or -EINPROGRESS
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* must be returned.
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*/
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if (ret)
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ret = -EINPROGRESS;
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if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
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fq->q.meat == fq->q.len) {
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unsigned long orefdst = skb->_skb_refdst;
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skb->_skb_refdst = 0UL;
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if (nf_ct_frag6_reasm(fq, skb, dev))
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ret = 0;
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skb->_skb_refdst = orefdst;
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} else {
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skb_dst_drop(skb);
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}
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out_unlock:
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spin_unlock_bh(&fq->q.lock);
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inet_frag_put(&fq->q);
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return ret;
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