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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>
This commit is contained in:
Ilpo Järvinen 2008-08-23 05:10:12 -07:00 committed by David S. Miller
parent 23edcc4147
commit cbe2d128a0
1 changed files with 69 additions and 78 deletions
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147
net/ipv4/tcp_input.c
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@ -4691,6 +4691,67 @@ out:
} }
#endif /* CONFIG_NET_DMA */ #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. * TCP receive function for the ESTABLISHED state.
* *
@ -4718,6 +4779,7 @@ int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
struct tcphdr *th, unsigned len) struct tcphdr *th, unsigned len)
{ {
struct tcp_sock *tp = tcp_sk(sk); struct tcp_sock *tp = tcp_sk(sk);
int res;
/* /*
* Header prediction. * Header prediction.
@ -4898,52 +4960,13 @@ slow_path:
if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb)) if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb))
goto csum_error; 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. * Standard slow path.
*/ */
if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { res = tcp_validate_incoming(sk, skb, th, 1);
/* RFC793, page 37: "In all states except SYN-SENT, all reset if (res <= 0)
* (RST) segments are validated by checking their SEQ-fields." return -res;
* 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;
}
step5: step5:
if (th->ack) if (th->ack)
@ -5225,6 +5248,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
struct tcp_sock *tp = tcp_sk(sk); struct tcp_sock *tp = tcp_sk(sk);
struct inet_connection_sock *icsk = inet_csk(sk); struct inet_connection_sock *icsk = inet_csk(sk);
int queued = 0; int queued = 0;
int res;
tp->rx_opt.saw_tstamp = 0; tp->rx_opt.saw_tstamp = 0;
@ -5277,42 +5301,9 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
return 0; return 0;
} }
if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp && res = tcp_validate_incoming(sk, skb, th, 0);
tcp_paws_discard(sk, skb)) { if (res <= 0)
if (!th->rst) { return -res;
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;
}
/* step 5: check the ACK field */ /* step 5: check the ACK field */
if (th->ack) { if (th->ack) {