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tcp: Add tcp_validate_incoming & put duplicated code there
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Large block of code duplication removed.

Sadly, the return value thing is a bit tricky here but it
seems the most sensible way to return positive from validator
on success rather than negative.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Ilpo Järvinen authored and David S. Miller committed Aug 23, 2008
1 parent 23edcc4 commit cbe2d12
Showing 1 changed file with 69 additions and 78 deletions.
147 changes: 69 additions & 78 deletions net/ipv4/tcp_input.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4691,6 +4691,67 @@ static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb,
}
#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.
*
Expand Down Expand Up @@ -4718,6 +4779,7 @@ 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.
Expand Down Expand Up @@ -4898,52 +4960,13 @@ int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb))
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)
Expand Down Expand Up @@ -5225,6 +5248,7 @@ 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;

Expand Down Expand Up @@ -5277,42 +5301,9 @@ 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) {
Expand Down

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