[PATCH 4.4 59/65] ip: use rb trees for IP frag queue.

4.4-stable review patch. If anyone has any objections, please let me know.

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From: Peter Oskolkov posk@google.com

commit fa0f527358bd900ef92f925878ed6bfbd51305cc upstream.

Similar to TCP OOO RX queue, it makes sense to use rb trees to store IP fragments, so that OOO fragments are inserted faster.

Tested:

- a follow-up patch contains a rather comprehensive ip defrag self-test (functional) - ran neper `udp_stream -c -H <host> -F 100 -l 300 -T 20`: netstat --statistics Ip: 282078937 total packets received 0 forwarded 0 incoming packets discarded 946760 incoming packets delivered 18743456 requests sent out 101 fragments dropped after timeout 282077129 reassemblies required 944952 packets reassembled ok 262734239 packet reassembles failed (The numbers/stats above are somewhat better re: reassemblies vs a kernel without this patchset. More comprehensive performance testing TBD).

Reported-by: Jann Horn jannh@google.com Reported-by: Juha-Matti Tilli juha-matti.tilli@iki.fi Suggested-by: Eric Dumazet edumazet@google.com Signed-off-by: Peter Oskolkov posk@google.com Signed-off-by: Eric Dumazet edumazet@google.com Cc: Florian Westphal fw@strlen.de Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Mao Wenan maowenan@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- include/linux/skbuff.h | 2 include/net/inet_frag.h | 3 net/ipv4/inet_fragment.c | 14 +- net/ipv4/ip_fragment.c | 190 +++++++++++++++++--------------- net/ipv6/netfilter/nf_conntrack_reasm.c | 1 net/ipv6/reassembly.c | 1 6 files changed, 120 insertions(+), 91 deletions(-)

--- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -556,7 +556,7 @@ struct sk_buff { struct skb_mstamp skb_mstamp; }; }; - struct rb_node rbnode; /* used in netem & tcp stack */ + struct rb_node rbnode; /* used in netem, ip4 defrag, and tcp stack */ }; struct sock *sk; struct net_device *dev; --- a/include/net/inet_frag.h +++ b/include/net/inet_frag.h @@ -45,7 +45,8 @@ struct inet_frag_queue { struct timer_list timer; struct hlist_node list; atomic_t refcnt; - struct sk_buff *fragments; + struct sk_buff *fragments; /* Used in IPv6. */ + struct rb_root rb_fragments; /* Used in IPv4. */ struct sk_buff *fragments_tail; ktime_t stamp; int len; --- a/net/ipv4/inet_fragment.c +++ b/net/ipv4/inet_fragment.c @@ -306,12 +306,16 @@ void inet_frag_destroy(struct inet_frag_ /* Release all fragment data. */ fp = q->fragments; nf = q->net; - while (fp) { - struct sk_buff *xp = fp->next; + if (fp) { + do { + struct sk_buff *xp = fp->next;

- sum_truesize += fp->truesize; - frag_kfree_skb(nf, f, fp); - fp = xp; + sum_truesize += fp->truesize; + kfree_skb(fp); + fp = xp; + } while (fp); + } else { + sum_truesize = skb_rbtree_purge(&q->rb_fragments); } sum = sum_truesize + f->qsize;

--- a/net/ipv4/ip_fragment.c +++ b/net/ipv4/ip_fragment.c @@ -194,7 +194,7 @@ static bool frag_expire_skip_icmp(u32 us */ static void ip_expire(unsigned long arg) { - struct sk_buff *clone, *head; + struct sk_buff *head = NULL; const struct iphdr *iph; struct net *net; struct ipq *qp; @@ -211,14 +211,31 @@ static void ip_expire(unsigned long arg)

ipq_kill(qp); IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS); - - head = qp->q.fragments; - IP_INC_STATS_BH(net, IPSTATS_MIB_REASMTIMEOUT);

- if (!(qp->q.flags & INET_FRAG_FIRST_IN) || !head) + if (!qp->q.flags & INET_FRAG_FIRST_IN) goto out;

+ /* sk_buff::dev and sk_buff::rbnode are unionized. So we + * pull the head out of the tree in order to be able to + * deal with head->dev. + */ + if (qp->q.fragments) { + head = qp->q.fragments; + qp->q.fragments = head->next; + } else { + head = skb_rb_first(&qp->q.rb_fragments); + if (!head) + goto out; + rb_erase(&head->rbnode, &qp->q.rb_fragments); + memset(&head->rbnode, 0, sizeof(head->rbnode)); + barrier(); + } + if (head == qp->q.fragments_tail) + qp->q.fragments_tail = NULL; + + sub_frag_mem_limit(qp->q.net, head->truesize); + head->dev = dev_get_by_index_rcu(net, qp->iif); if (!head->dev) goto out; @@ -237,20 +254,17 @@ static void ip_expire(unsigned long arg) (skb_rtable(head)->rt_type != RTN_LOCAL)) goto out;

- clone = skb_clone(head, GFP_ATOMIC); - /* Send an ICMP "Fragment Reassembly Timeout" message. */ - if (clone) { - spin_unlock(&qp->q.lock); - icmp_send(clone, ICMP_TIME_EXCEEDED, - ICMP_EXC_FRAGTIME, 0); - consume_skb(clone); - goto out_rcu_unlock; - } + spin_unlock(&qp->q.lock); + icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0); + goto out_rcu_unlock; + out: spin_unlock(&qp->q.lock); out_rcu_unlock: rcu_read_unlock(); + if (head) + kfree_skb(head); ipq_put(qp); }

@@ -294,7 +308,7 @@ static int ip_frag_too_far(struct ipq *q end = atomic_inc_return(&peer->rid); qp->rid = end;

- rc = qp->q.fragments && (end - start) > max; + rc = qp->q.fragments_tail && (end - start) > max;

if (rc) { struct net *net; @@ -308,7 +322,6 @@ static int ip_frag_too_far(struct ipq *q

static int ip_frag_reinit(struct ipq *qp) { - struct sk_buff *fp; unsigned int sum_truesize = 0;

if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) { @@ -316,20 +329,14 @@ static int ip_frag_reinit(struct ipq *qp return -ETIMEDOUT; }

- fp = qp->q.fragments; - do { - struct sk_buff *xp = fp->next; - - sum_truesize += fp->truesize; - kfree_skb(fp); - fp = xp; - } while (fp); + sum_truesize = skb_rbtree_purge(&qp->q.rb_fragments); sub_frag_mem_limit(qp->q.net, sum_truesize);

qp->q.flags = 0; qp->q.len = 0; qp->q.meat = 0; qp->q.fragments = NULL; + qp->q.rb_fragments = RB_ROOT; qp->q.fragments_tail = NULL; qp->iif = 0; qp->ecn = 0; @@ -341,7 +348,8 @@ static int ip_frag_reinit(struct ipq *qp static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb) { struct net *net = container_of(qp->q.net, struct net, ipv4.frags); - struct sk_buff *prev, *next; + struct rb_node **rbn, *parent; + struct sk_buff *skb1; struct net_device *dev; unsigned int fragsize; int flags, offset; @@ -404,56 +412,60 @@ static int ip_frag_queue(struct ipq *qp, if (err) goto err;

- /* Find out which fragments are in front and at the back of us - * in the chain of fragments so far. We must know where to put - * this fragment, right? - */ - prev = qp->q.fragments_tail; - if (!prev || FRAG_CB(prev)->offset < offset) { - next = NULL; - goto found; - } - prev = NULL; - for (next = qp->q.fragments; next != NULL; next = next->next) { - if (FRAG_CB(next)->offset >= offset) - break; /* bingo! */ - prev = next; - } + /* Note : skb->rbnode and skb->dev share the same location. */ + dev = skb->dev; + /* Makes sure compiler wont do silly aliasing games */ + barrier();

-found: /* RFC5722, Section 4, amended by Errata ID : 3089 * When reassembling an IPv6 datagram, if * one or more its constituent fragments is determined to be an * overlapping fragment, the entire datagram (and any constituent * fragments) MUST be silently discarded. * - * We do the same here for IPv4. + * We do the same here for IPv4 (and increment an snmp counter). */ - /* Is there an overlap with the previous fragment? */ - if (prev && - (FRAG_CB(prev)->offset + prev->len) > offset) - goto discard_qp; - - /* Is there an overlap with the next fragment? */ - if (next && FRAG_CB(next)->offset < end) - goto discard_qp; - - FRAG_CB(skb)->offset = offset;

- /* Insert this fragment in the chain of fragments. */ - skb->next = next; - if (!next) + /* Find out where to put this fragment. */ + skb1 = qp->q.fragments_tail; + if (!skb1) { + /* This is the first fragment we've received. */ + rb_link_node(&skb->rbnode, NULL, &qp->q.rb_fragments.rb_node); + qp->q.fragments_tail = skb; + } else if ((FRAG_CB(skb1)->offset + skb1->len) < end) { + /* This is the common/special case: skb goes to the end. */ + /* Detect and discard overlaps. */ + if (offset < (FRAG_CB(skb1)->offset + skb1->len)) + goto discard_qp; + /* Insert after skb1. */ + rb_link_node(&skb->rbnode, &skb1->rbnode, &skb1->rbnode.rb_right); qp->q.fragments_tail = skb; - if (prev) - prev->next = skb; - else - qp->q.fragments = skb; + } else { + /* Binary search. Note that skb can become the first fragment, but + * not the last (covered above). */ + rbn = &qp->q.rb_fragments.rb_node; + do { + parent = *rbn; + skb1 = rb_to_skb(parent); + if (end <= FRAG_CB(skb1)->offset) + rbn = &parent->rb_left; + else if (offset >= FRAG_CB(skb1)->offset + skb1->len) + rbn = &parent->rb_right; + else /* Found an overlap with skb1. */ + goto discard_qp; + } while (*rbn); + /* Here we have parent properly set, and rbn pointing to + * one of its NULL left/right children. Insert skb. */ + rb_link_node(&skb->rbnode, parent, rbn); + } + rb_insert_color(&skb->rbnode, &qp->q.rb_fragments);

- dev = skb->dev; if (dev) { qp->iif = dev->ifindex; skb->dev = NULL; } + FRAG_CB(skb)->offset = offset; + qp->q.stamp = skb->tstamp; qp->q.meat += skb->len; qp->ecn |= ecn; @@ -475,7 +487,7 @@ found: unsigned long orefdst = skb->_skb_refdst;

skb->_skb_refdst = 0UL; - err = ip_frag_reasm(qp, prev, dev); + err = ip_frag_reasm(qp, skb, dev); skb->_skb_refdst = orefdst; return err; } @@ -492,15 +504,15 @@ err: return err; }

- /* Build a new IP datagram from all its fragments. */ - -static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev, +static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb, struct net_device *dev) { struct net *net = container_of(qp->q.net, struct net, ipv4.frags); struct iphdr *iph; - struct sk_buff *fp, *head = qp->q.fragments; + struct sk_buff *fp, *head = skb_rb_first(&qp->q.rb_fragments); + struct sk_buff **nextp; /* To build frag_list. */ + struct rb_node *rbn; int len; int ihlen; int err; @@ -514,25 +526,21 @@ static int ip_frag_reasm(struct ipq *qp, goto out_fail; } /* Make the one we just received the head. */ - if (prev) { - head = prev->next; - fp = skb_clone(head, GFP_ATOMIC); + if (head != skb) { + fp = skb_clone(skb, GFP_ATOMIC); if (!fp) goto out_nomem;

- fp->next = head->next; - if (!fp->next) + rb_replace_node(&skb->rbnode, &fp->rbnode, &qp->q.rb_fragments); + if (qp->q.fragments_tail == skb) qp->q.fragments_tail = fp; - prev->next = fp; - - skb_morph(head, qp->q.fragments); - head->next = qp->q.fragments->next; - - consume_skb(qp->q.fragments); - qp->q.fragments = head; + skb_morph(skb, head); + rb_replace_node(&head->rbnode, &skb->rbnode, + &qp->q.rb_fragments); + consume_skb(head); + head = skb; }

- WARN_ON(!head); WARN_ON(FRAG_CB(head)->offset != 0);

/* Allocate a new buffer for the datagram. */ @@ -557,24 +565,35 @@ static int ip_frag_reasm(struct ipq *qp, clone = alloc_skb(0, GFP_ATOMIC); if (!clone) goto out_nomem; - clone->next = head->next; - head->next = clone; skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list; skb_frag_list_init(head); for (i = 0; i < skb_shinfo(head)->nr_frags; i++) plen += skb_frag_size(&skb_shinfo(head)->frags[i]); clone->len = clone->data_len = head->data_len - plen; - head->data_len -= clone->len; - head->len -= clone->len; + skb->truesize += clone->truesize; clone->csum = 0; clone->ip_summed = head->ip_summed; add_frag_mem_limit(qp->q.net, clone->truesize); + skb_shinfo(head)->frag_list = clone; + nextp = &clone->next; + } else { + nextp = &skb_shinfo(head)->frag_list; }

- skb_shinfo(head)->frag_list = head->next; skb_push(head, head->data - skb_network_header(head));

- for (fp=head->next; fp; fp = fp->next) { + /* Traverse the tree in order, to build frag_list. */ + rbn = rb_next(&head->rbnode); + rb_erase(&head->rbnode, &qp->q.rb_fragments); + while (rbn) { + struct rb_node *rbnext = rb_next(rbn); + fp = rb_to_skb(rbn); + rb_erase(rbn, &qp->q.rb_fragments); + rbn = rbnext; + *nextp = fp; + nextp = &fp->next; + fp->prev = NULL; + memset(&fp->rbnode, 0, sizeof(fp->rbnode)); head->data_len += fp->len; head->len += fp->len; if (head->ip_summed != fp->ip_summed) @@ -585,7 +604,9 @@ static int ip_frag_reasm(struct ipq *qp, } sub_frag_mem_limit(qp->q.net, head->truesize);

+ *nextp = NULL; head->next = NULL; + head->prev = NULL; head->dev = dev; head->tstamp = qp->q.stamp; IPCB(head)->frag_max_size = max(qp->max_df_size, qp->q.max_size); @@ -613,6 +634,7 @@ static int ip_frag_reasm(struct ipq *qp,

IP_INC_STATS_BH(net, IPSTATS_MIB_REASMOKS); qp->q.fragments = NULL; + qp->q.rb_fragments = RB_ROOT; qp->q.fragments_tail = NULL; return 0;

--- a/net/ipv6/netfilter/nf_conntrack_reasm.c +++ b/net/ipv6/netfilter/nf_conntrack_reasm.c @@ -472,6 +472,7 @@ nf_ct_frag6_reasm(struct frag_queue *fq, head->csum);

fq->q.fragments = NULL; + fq->q.rb_fragments = RB_ROOT; fq->q.fragments_tail = NULL;

/* all original skbs are linked into the NFCT_FRAG6_CB(head).orig */ --- a/net/ipv6/reassembly.c +++ b/net/ipv6/reassembly.c @@ -499,6 +499,7 @@ static int ip6_frag_reasm(struct frag_qu IP6_INC_STATS_BH(net, __in6_dev_get(dev), IPSTATS_MIB_REASMOKS); rcu_read_unlock(); fq->q.fragments = NULL; + fq->q.rb_fragments = RB_ROOT; fq->q.fragments_tail = NULL; return 1;