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Diffstat (limited to 'net/ipv4/tcp_input.c')
-rw-r--r--net/ipv4/tcp_input.c332
1 files changed, 170 insertions, 162 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 67ccce2a96bd..d77c0d29e239 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -979,6 +979,39 @@ static void tcp_update_reordering(struct sock *sk, const int metric,
}
}
+/* This must be called before lost_out is incremented */
+static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb)
+{
+ if ((tp->retransmit_skb_hint == NULL) ||
+ before(TCP_SKB_CB(skb)->seq,
+ TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
+ tp->retransmit_skb_hint = skb;
+
+ if (!tp->lost_out ||
+ after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high))
+ tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
+}
+
+static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb)
+{
+ if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
+ tcp_verify_retransmit_hint(tp, skb);
+
+ tp->lost_out += tcp_skb_pcount(skb);
+ TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
+ }
+}
+
+void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, struct sk_buff *skb)
+{
+ tcp_verify_retransmit_hint(tp, skb);
+
+ if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
+ tp->lost_out += tcp_skb_pcount(skb);
+ TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
+ }
+}
+
/* This procedure tags the retransmission queue when SACKs arrive.
*
* We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
@@ -1155,13 +1188,7 @@ static void tcp_mark_lost_retrans(struct sock *sk)
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
tp->retrans_out -= tcp_skb_pcount(skb);
- /* clear lost hint */
- tp->retransmit_skb_hint = NULL;
-
- if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
- tp->lost_out += tcp_skb_pcount(skb);
- TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
- }
+ tcp_skb_mark_lost_uncond_verify(tp, skb);
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT);
} else {
if (before(ack_seq, new_low_seq))
@@ -1271,9 +1298,6 @@ static int tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
tp->lost_out -= tcp_skb_pcount(skb);
tp->retrans_out -= tcp_skb_pcount(skb);
-
- /* clear lost hint */
- tp->retransmit_skb_hint = NULL;
}
} else {
if (!(sacked & TCPCB_RETRANS)) {
@@ -1292,9 +1316,6 @@ static int tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
if (sacked & TCPCB_LOST) {
TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
tp->lost_out -= tcp_skb_pcount(skb);
-
- /* clear lost hint */
- tp->retransmit_skb_hint = NULL;
}
}
@@ -1324,7 +1345,6 @@ static int tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
if (dup_sack && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)) {
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
tp->retrans_out -= tcp_skb_pcount(skb);
- tp->retransmit_skb_hint = NULL;
}
return flag;
@@ -1726,6 +1746,8 @@ int tcp_use_frto(struct sock *sk)
return 0;
skb = tcp_write_queue_head(sk);
+ if (tcp_skb_is_last(sk, skb))
+ return 1;
skb = tcp_write_queue_next(sk, skb); /* Skips head */
tcp_for_write_queue_from(skb, sk) {
if (skb == tcp_send_head(sk))
@@ -1867,6 +1889,7 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
tp->lost_out += tcp_skb_pcount(skb);
+ tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
}
}
tcp_verify_left_out(tp);
@@ -1883,7 +1906,7 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
tp->high_seq = tp->snd_nxt;
TCP_ECN_queue_cwr(tp);
- tcp_clear_retrans_hints_partial(tp);
+ tcp_clear_all_retrans_hints(tp);
}
static void tcp_clear_retrans_partial(struct tcp_sock *tp)
@@ -1934,12 +1957,11 @@ void tcp_enter_loss(struct sock *sk, int how)
/* Push undo marker, if it was plain RTO and nothing
* was retransmitted. */
tp->undo_marker = tp->snd_una;
- tcp_clear_retrans_hints_partial(tp);
} else {
tp->sacked_out = 0;
tp->fackets_out = 0;
- tcp_clear_all_retrans_hints(tp);
}
+ tcp_clear_all_retrans_hints(tp);
tcp_for_write_queue(skb, sk) {
if (skb == tcp_send_head(sk))
@@ -1952,6 +1974,7 @@ void tcp_enter_loss(struct sock *sk, int how)
TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
tp->lost_out += tcp_skb_pcount(skb);
+ tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
}
}
tcp_verify_left_out(tp);
@@ -2157,19 +2180,6 @@ static int tcp_time_to_recover(struct sock *sk)
return 0;
}
-/* RFC: This is from the original, I doubt that this is necessary at all:
- * clear xmit_retrans hint if seq of this skb is beyond hint. How could we
- * retransmitted past LOST markings in the first place? I'm not fully sure
- * about undo and end of connection cases, which can cause R without L?
- */
-static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb)
-{
- if ((tp->retransmit_skb_hint != NULL) &&
- before(TCP_SKB_CB(skb)->seq,
- TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
- tp->retransmit_skb_hint = NULL;
-}
-
/* Mark head of queue up as lost. With RFC3517 SACK, the packets is
* is against sacked "cnt", otherwise it's against facked "cnt"
*/
@@ -2217,11 +2227,7 @@ static void tcp_mark_head_lost(struct sock *sk, int packets)
cnt = packets;
}
- if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_SACKED_ACKED|TCPCB_LOST))) {
- TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
- tp->lost_out += tcp_skb_pcount(skb);
- tcp_verify_retransmit_hint(tp, skb);
- }
+ tcp_skb_mark_lost(tp, skb);
}
tcp_verify_left_out(tp);
}
@@ -2263,11 +2269,7 @@ static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit)
if (!tcp_skb_timedout(sk, skb))
break;
- if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_SACKED_ACKED|TCPCB_LOST))) {
- TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
- tp->lost_out += tcp_skb_pcount(skb);
- tcp_verify_retransmit_hint(tp, skb);
- }
+ tcp_skb_mark_lost(tp, skb);
}
tp->scoreboard_skb_hint = skb;
@@ -2378,10 +2380,6 @@ static void tcp_undo_cwr(struct sock *sk, const int undo)
}
tcp_moderate_cwnd(tp);
tp->snd_cwnd_stamp = tcp_time_stamp;
-
- /* There is something screwy going on with the retrans hints after
- an undo */
- tcp_clear_all_retrans_hints(tp);
}
static inline int tcp_may_undo(struct tcp_sock *tp)
@@ -2838,7 +2836,8 @@ static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb)
* is before the ack sequence we can discard it as it's confirmed to have
* arrived at the other end.
*/
-static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
+static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
+ u32 prior_snd_una)
{
struct tcp_sock *tp = tcp_sk(sk);
const struct inet_connection_sock *icsk = inet_csk(sk);
@@ -2848,6 +2847,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
int flag = 0;
u32 pkts_acked = 0;
u32 reord = tp->packets_out;
+ u32 prior_sacked = tp->sacked_out;
s32 seq_rtt = -1;
s32 ca_seq_rtt = -1;
ktime_t last_ackt = net_invalid_timestamp();
@@ -2904,9 +2904,6 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
if (sacked & TCPCB_LOST)
tp->lost_out -= acked_pcount;
- if (unlikely(tp->urg_mode && !before(end_seq, tp->snd_up)))
- tp->urg_mode = 0;
-
tp->packets_out -= acked_pcount;
pkts_acked += acked_pcount;
@@ -2929,9 +2926,16 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
tcp_unlink_write_queue(skb, sk);
sk_wmem_free_skb(sk, skb);
- tcp_clear_all_retrans_hints(tp);
+ tp->scoreboard_skb_hint = NULL;
+ if (skb == tp->retransmit_skb_hint)
+ tp->retransmit_skb_hint = NULL;
+ if (skb == tp->lost_skb_hint)
+ tp->lost_skb_hint = NULL;
}
+ if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una)))
+ tp->snd_up = tp->snd_una;
+
if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
flag |= FLAG_SACK_RENEGING;
@@ -2948,6 +2952,15 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
/* Non-retransmitted hole got filled? That's reordering */
if (reord < prior_fackets)
tcp_update_reordering(sk, tp->fackets_out - reord, 0);
+
+ /* No need to care for underflows here because
+ * the lost_skb_hint gets NULLed if we're past it
+ * (or something non-trivial happened)
+ */
+ if (tcp_is_fack(tp))
+ tp->lost_cnt_hint -= pkts_acked;
+ else
+ tp->lost_cnt_hint -= prior_sacked - tp->sacked_out;
}
tp->fackets_out -= min(pkts_acked, tp->fackets_out);
@@ -3299,7 +3312,7 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
goto no_queue;
/* See if we can take anything off of the retransmit queue. */
- flag |= tcp_clean_rtx_queue(sk, prior_fackets);
+ flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una);
if (tp->frto_counter)
frto_cwnd = tcp_process_frto(sk, flag);
@@ -3442,6 +3455,22 @@ void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx,
}
}
+static int tcp_parse_aligned_timestamp(struct tcp_sock *tp, struct tcphdr *th)
+{
+ __be32 *ptr = (__be32 *)(th + 1);
+
+ if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
+ | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
+ tp->rx_opt.saw_tstamp = 1;
+ ++ptr;
+ tp->rx_opt.rcv_tsval = ntohl(*ptr);
+ ++ptr;
+ tp->rx_opt.rcv_tsecr = ntohl(*ptr);
+ return 1;
+ }
+ return 0;
+}
+
/* Fast parse options. This hopes to only see timestamps.
* If it is wrong it falls back on tcp_parse_options().
*/
@@ -3453,16 +3482,8 @@ static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
return 0;
} else if (tp->rx_opt.tstamp_ok &&
th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) {
- __be32 *ptr = (__be32 *)(th + 1);
- if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
- | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
- tp->rx_opt.saw_tstamp = 1;
- ++ptr;
- tp->rx_opt.rcv_tsval = ntohl(*ptr);
- ++ptr;
- tp->rx_opt.rcv_tsecr = ntohl(*ptr);
+ if (tcp_parse_aligned_timestamp(tp, th))
return 1;
- }
}
tcp_parse_options(skb, &tp->rx_opt, 1);
return 1;
@@ -4138,7 +4159,7 @@ drop:
skb1 = skb1->prev;
}
}
- __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue);
+ __skb_queue_after(&tp->out_of_order_queue, skb1, skb);
/* And clean segments covered by new one as whole. */
while ((skb1 = skb->next) !=
@@ -4161,6 +4182,18 @@ add_sack:
}
}
+static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb,
+ struct sk_buff_head *list)
+{
+ struct sk_buff *next = skb->next;
+
+ __skb_unlink(skb, list);
+ __kfree_skb(skb);
+ NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED);
+
+ return next;
+}
+
/* Collapse contiguous sequence of skbs head..tail with
* sequence numbers start..end.
* Segments with FIN/SYN are not collapsed (only because this
@@ -4178,11 +4211,7 @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list,
for (skb = head; skb != tail;) {
/* No new bits? It is possible on ofo queue. */
if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
- struct sk_buff *next = skb->next;
- __skb_unlink(skb, list);
- __kfree_skb(skb);
- NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED);
- skb = next;
+ skb = tcp_collapse_one(sk, skb, list);
continue;
}
@@ -4228,7 +4257,7 @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list,
memcpy(nskb->head, skb->head, header);
memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
- __skb_insert(nskb, skb->prev, skb, list);
+ __skb_queue_before(list, skb, nskb);
skb_set_owner_r(nskb, sk);
/* Copy data, releasing collapsed skbs. */
@@ -4246,11 +4275,7 @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list,
start += size;
}
if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
- struct sk_buff *next = skb->next;
- __skb_unlink(skb, list);
- __kfree_skb(skb);
- NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED);
- skb = next;
+ skb = tcp_collapse_one(sk, skb, list);
if (skb == tail ||
tcp_hdr(skb)->syn ||
tcp_hdr(skb)->fin)
@@ -4436,8 +4461,8 @@ static void tcp_new_space(struct sock *sk)
if (tcp_should_expand_sndbuf(sk)) {
int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
- MAX_TCP_HEADER + 16 + sizeof(struct sk_buff),
- demanded = max_t(unsigned int, tp->snd_cwnd,
+ MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
+ int demanded = max_t(unsigned int, tp->snd_cwnd,
tp->reordering + 1);
sndmem *= 2 * demanded;
if (sndmem > sk->sk_sndbuf)
@@ -4691,6 +4716,67 @@ out:
}
#endif /* CONFIG_NET_DMA */
+/* Does PAWS and seqno based validation of an incoming segment, flags will
+ * play significant role here.
+ */
+static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
+ struct tcphdr *th, int syn_inerr)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ /* RFC1323: H1. Apply PAWS check first. */
+ if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
+ tcp_paws_discard(sk, skb)) {
+ if (!th->rst) {
+ NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
+ tcp_send_dupack(sk, skb);
+ goto discard;
+ }
+ /* Reset is accepted even if it did not pass PAWS. */
+ }
+
+ /* Step 1: check sequence number */
+ if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
+ /* RFC793, page 37: "In all states except SYN-SENT, all reset
+ * (RST) segments are validated by checking their SEQ-fields."
+ * And page 69: "If an incoming segment is not acceptable,
+ * an acknowledgment should be sent in reply (unless the RST
+ * bit is set, if so drop the segment and return)".
+ */
+ if (!th->rst)
+ tcp_send_dupack(sk, skb);
+ goto discard;
+ }
+
+ /* Step 2: check RST bit */
+ if (th->rst) {
+ tcp_reset(sk);
+ goto discard;
+ }
+
+ /* ts_recent update must be made after we are sure that the packet
+ * is in window.
+ */
+ tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
+
+ /* step 3: check security and precedence [ignored] */
+
+ /* step 4: Check for a SYN in window. */
+ if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
+ if (syn_inerr)
+ TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
+ NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN);
+ tcp_reset(sk);
+ return -1;
+ }
+
+ return 1;
+
+discard:
+ __kfree_skb(skb);
+ return 0;
+}
+
/*
* TCP receive function for the ESTABLISHED state.
*
@@ -4718,6 +4804,7 @@ int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
struct tcphdr *th, unsigned len)
{
struct tcp_sock *tp = tcp_sk(sk);
+ int res;
/*
* Header prediction.
@@ -4756,19 +4843,10 @@ int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
/* Check timestamp */
if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
- __be32 *ptr = (__be32 *)(th + 1);
-
/* No? Slow path! */
- if (*ptr != htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
- | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP))
+ if (!tcp_parse_aligned_timestamp(tp, th))
goto slow_path;
- tp->rx_opt.saw_tstamp = 1;
- ++ptr;
- tp->rx_opt.rcv_tsval = ntohl(*ptr);
- ++ptr;
- tp->rx_opt.rcv_tsecr = ntohl(*ptr);
-
/* If PAWS failed, check it more carefully in slow path */
if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
goto slow_path;
@@ -4879,7 +4957,8 @@ int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
goto no_ack;
}
- __tcp_ack_snd_check(sk, 0);
+ if (!copied_early || tp->rcv_nxt != tp->rcv_wup)
+ __tcp_ack_snd_check(sk, 0);
no_ack:
#ifdef CONFIG_NET_DMA
if (copied_early)
@@ -4899,51 +4978,12 @@ slow_path:
goto csum_error;
/*
- * RFC1323: H1. Apply PAWS check first.
- */
- if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
- tcp_paws_discard(sk, skb)) {
- if (!th->rst) {
- NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
- tcp_send_dupack(sk, skb);
- goto discard;
- }
- /* Resets are accepted even if PAWS failed.
-
- ts_recent update must be made after we are sure
- that the packet is in window.
- */
- }
-
- /*
* Standard slow path.
*/
- if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
- /* RFC793, page 37: "In all states except SYN-SENT, all reset
- * (RST) segments are validated by checking their SEQ-fields."
- * And page 69: "If an incoming segment is not acceptable,
- * an acknowledgment should be sent in reply (unless the RST bit
- * is set, if so drop the segment and return)".
- */
- if (!th->rst)
- tcp_send_dupack(sk, skb);
- goto discard;
- }
-
- if (th->rst) {
- tcp_reset(sk);
- goto discard;
- }
-
- tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
-
- if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
- TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
- NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN);
- tcp_reset(sk);
- return 1;
- }
+ res = tcp_validate_incoming(sk, skb, th, 1);
+ if (res <= 0)
+ return -res;
step5:
if (th->ack)
@@ -5225,6 +5265,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
struct tcp_sock *tp = tcp_sk(sk);
struct inet_connection_sock *icsk = inet_csk(sk);
int queued = 0;
+ int res;
tp->rx_opt.saw_tstamp = 0;
@@ -5277,42 +5318,9 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
return 0;
}
- if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
- tcp_paws_discard(sk, skb)) {
- if (!th->rst) {
- NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
- tcp_send_dupack(sk, skb);
- goto discard;
- }
- /* Reset is accepted even if it did not pass PAWS. */
- }
-
- /* step 1: check sequence number */
- if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
- if (!th->rst)
- tcp_send_dupack(sk, skb);
- goto discard;
- }
-
- /* step 2: check RST bit */
- if (th->rst) {
- tcp_reset(sk);
- goto discard;
- }
-
- tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
-
- /* step 3: check security and precedence [ignored] */
-
- /* step 4:
- *
- * Check for a SYN in window.
- */
- if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
- NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN);
- tcp_reset(sk);
- return 1;
- }
+ res = tcp_validate_incoming(sk, skb, th, 0);
+ if (res <= 0)
+ return -res;
/* step 5: check the ACK field */
if (th->ack) {