tcp: introduce tcp_data_queue_ofo

Split tcp_data_queue() in two parts for better readability.

tcp_data_queue_ofo() is responsible for queueing incoming skb into out
of order queue.

Change code layout so that the skb_set_owner_r() is performed only if
skb is not dropped.

This is a preliminary patch before "reduce out_of_order memory use"
following patch.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: H.K. Jerry Chu <hkchu@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 115 insertions, 99 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 68d4057cba00..fa7de12c4a52 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4446,6 +4446,120 @@ static inline int tcp_try_rmem_schedule(struct sock *sk, unsigned int size)
         return 0;
 }
 
+static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
+{
+        struct tcp_sock *tp = tcp_sk(sk);
+        struct sk_buff *skb1;
+        u32 seq, end_seq;
+
+        TCP_ECN_check_ce(tp, skb);
+
+        if (tcp_try_rmem_schedule(sk, skb->truesize)) {
+                /* TODO: should increment a counter */
+                __kfree_skb(skb);
+                return;
+        }
+
+        /* Disable header prediction. */
+        tp->pred_flags = 0;
+        inet_csk_schedule_ack(sk);
+
+        SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
+                   tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
+
+        skb1 = skb_peek_tail(&tp->out_of_order_queue);
+        if (!skb1) {
+                /* Initial out of order segment, build 1 SACK. */
+                if (tcp_is_sack(tp)) {
+                        tp->rx_opt.num_sacks = 1;
+                        tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
+                        tp->selective_acks[0].end_seq =
+                                                TCP_SKB_CB(skb)->end_seq;
+                }
+                __skb_queue_head(&tp->out_of_order_queue, skb);
+                goto end;
+        }
+
+        seq = TCP_SKB_CB(skb)->seq;
+        end_seq = TCP_SKB_CB(skb)->end_seq;
+
+        if (seq == TCP_SKB_CB(skb1)->end_seq) {
+                __skb_queue_after(&tp->out_of_order_queue, skb1, skb);
+
+                if (!tp->rx_opt.num_sacks ||
+                    tp->selective_acks[0].end_seq != seq)
+                        goto add_sack;
+
+                /* Common case: data arrive in order after hole. */
+                tp->selective_acks[0].end_seq = end_seq;
+                goto end;
+        }
+
+        /* Find place to insert this segment. */
+        while (1) {
+                if (!after(TCP_SKB_CB(skb1)->seq, seq))
+                        break;
+                if (skb_queue_is_first(&tp->out_of_order_queue, skb1)) {
+                        skb1 = NULL;
+                        break;
+                }
+                skb1 = skb_queue_prev(&tp->out_of_order_queue, skb1);
+        }
+
+        /* Do skb overlap to previous one? */
+        if (skb1 && before(seq, TCP_SKB_CB(skb1)->end_seq)) {
+                if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
+                        /* All the bits are present. Drop. */
+                        __kfree_skb(skb);
+                        skb = NULL;
+                        tcp_dsack_set(sk, seq, end_seq);
+                        goto add_sack;
+                }
+                if (after(seq, TCP_SKB_CB(skb1)->seq)) {
+                        /* Partial overlap. */
+                        tcp_dsack_set(sk, seq,
+                                      TCP_SKB_CB(skb1)->end_seq);
+                } else {
+                        if (skb_queue_is_first(&tp->out_of_order_queue,
+                                               skb1))
+                                skb1 = NULL;
+                        else
+                                skb1 = skb_queue_prev(
+                                        &tp->out_of_order_queue,
+                                        skb1);
+                }
+        }
+        if (!skb1)
+                __skb_queue_head(&tp->out_of_order_queue, skb);
+        else
+                __skb_queue_after(&tp->out_of_order_queue, skb1, skb);
+
+        /* And clean segments covered by new one as whole. */
+        while (!skb_queue_is_last(&tp->out_of_order_queue, skb)) {
+                skb1 = skb_queue_next(&tp->out_of_order_queue, skb);
+
+                if (!after(end_seq, TCP_SKB_CB(skb1)->seq))
+                        break;
+                if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
+                        tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
+                                         end_seq);
+                        break;
+                }
+                __skb_unlink(skb1, &tp->out_of_order_queue);
+                tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
+                                 TCP_SKB_CB(skb1)->end_seq);
+                __kfree_skb(skb1);
+        }
+
+add_sack:
+        if (tcp_is_sack(tp))
+                tcp_sack_new_ofo_skb(sk, seq, end_seq);
+end:
+        if (skb)
+                skb_set_owner_r(skb, sk);
+}
+
+
 static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 {
         const struct tcphdr *th = tcp_hdr(skb);
@@ -4561,105 +4675,7 @@ drop:
                 goto queue_and_out;
         }
 
-        TCP_ECN_check_ce(tp, skb);
-
-        if (tcp_try_rmem_schedule(sk, skb->truesize))
-                goto drop;
-
-        /* Disable header prediction. */
-        tp->pred_flags = 0;
-        inet_csk_schedule_ack(sk);
-
-        SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
-                   tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
-
-        skb_set_owner_r(skb, sk);
-
-        if (!skb_peek(&tp->out_of_order_queue)) {
-                /* Initial out of order segment, build 1 SACK. */
-                if (tcp_is_sack(tp)) {
-                        tp->rx_opt.num_sacks = 1;
-                        tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
-                        tp->selective_acks[0].end_seq =
-                                                TCP_SKB_CB(skb)->end_seq;
-                }
-                __skb_queue_head(&tp->out_of_order_queue, skb);
-        } else {
-                struct sk_buff *skb1 = skb_peek_tail(&tp->out_of_order_queue);
-                u32 seq = TCP_SKB_CB(skb)->seq;
-                u32 end_seq = TCP_SKB_CB(skb)->end_seq;
-
-                if (seq == TCP_SKB_CB(skb1)->end_seq) {
-                        __skb_queue_after(&tp->out_of_order_queue, skb1, skb);
-
-                        if (!tp->rx_opt.num_sacks ||
-                            tp->selective_acks[0].end_seq != seq)
-                                goto add_sack;
-
-                        /* Common case: data arrive in order after hole. */
-                        tp->selective_acks[0].end_seq = end_seq;
-                        return;
-                }
-
-                /* Find place to insert this segment. */
-                while (1) {
-                        if (!after(TCP_SKB_CB(skb1)->seq, seq))
-                                break;
-                        if (skb_queue_is_first(&tp->out_of_order_queue, skb1)) {
-                                skb1 = NULL;
-                                break;
-                        }
-                        skb1 = skb_queue_prev(&tp->out_of_order_queue, skb1);
-                }
-
-                /* Do skb overlap to previous one? */
-                if (skb1 && before(seq, TCP_SKB_CB(skb1)->end_seq)) {
-                        if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
-                                /* All the bits are present. Drop. */
-                                __kfree_skb(skb);
-                                tcp_dsack_set(sk, seq, end_seq);
-                                goto add_sack;
-                        }
-                        if (after(seq, TCP_SKB_CB(skb1)->seq)) {
-                                /* Partial overlap. */
-                                tcp_dsack_set(sk, seq,
-                                              TCP_SKB_CB(skb1)->end_seq);
-                        } else {
-                                if (skb_queue_is_first(&tp->out_of_order_queue,
-                                                       skb1))
-                                        skb1 = NULL;
-                                else
-                                        skb1 = skb_queue_prev(
-                                                &tp->out_of_order_queue,
-                                                skb1);
-                        }
-                }
-                if (!skb1)
-                        __skb_queue_head(&tp->out_of_order_queue, skb);
-                else
-                        __skb_queue_after(&tp->out_of_order_queue, skb1, skb);
-
-                /* And clean segments covered by new one as whole. */
-                while (!skb_queue_is_last(&tp->out_of_order_queue, skb)) {
-                        skb1 = skb_queue_next(&tp->out_of_order_queue, skb);
-
-                        if (!after(end_seq, TCP_SKB_CB(skb1)->seq))
-                                break;
-                        if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
-                                tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
-                                                 end_seq);
-                                break;
-                        }
-                        __skb_unlink(skb1, &tp->out_of_order_queue);
-                        tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
-                                         TCP_SKB_CB(skb1)->end_seq);
-                        __kfree_skb(skb1);
-                }
-
-add_sack:
-                if (tcp_is_sack(tp))
-                        tcp_sack_new_ofo_skb(sk, seq, end_seq);
-        }
+        tcp_data_queue_ofo(sk, skb);
 }
 
 static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb,