tcp: Add tcp_validate_incoming & put duplicated code there
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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@ -4691,6 +4691,67 @@ out:
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}
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#endif /* CONFIG_NET_DMA */
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/* Does PAWS and seqno based validation of an incoming segment, flags will
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* play significant role here.
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*/
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static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
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struct tcphdr *th, int syn_inerr)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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/* RFC1323: H1. Apply PAWS check first. */
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if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
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tcp_paws_discard(sk, skb)) {
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if (!th->rst) {
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NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
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tcp_send_dupack(sk, skb);
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goto discard;
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}
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/* Reset is accepted even if it did not pass PAWS. */
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}
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/* Step 1: check sequence number */
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if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
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/* RFC793, page 37: "In all states except SYN-SENT, all reset
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* (RST) segments are validated by checking their SEQ-fields."
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* And page 69: "If an incoming segment is not acceptable,
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* an acknowledgment should be sent in reply (unless the RST
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* bit is set, if so drop the segment and return)".
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*/
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if (!th->rst)
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tcp_send_dupack(sk, skb);
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goto discard;
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}
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/* Step 2: check RST bit */
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if (th->rst) {
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tcp_reset(sk);
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goto discard;
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}
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/* ts_recent update must be made after we are sure that the packet
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* is in window.
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*/
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tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
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/* step 3: check security and precedence [ignored] */
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/* step 4: Check for a SYN in window. */
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if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
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if (syn_inerr)
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TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
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NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN);
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tcp_reset(sk);
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return -1;
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}
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return 1;
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discard:
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__kfree_skb(skb);
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return 0;
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}
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/*
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* TCP receive function for the ESTABLISHED state.
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*
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@ -4718,6 +4779,7 @@ int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
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struct tcphdr *th, unsigned len)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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int res;
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/*
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* Header prediction.
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@ -4898,52 +4960,13 @@ slow_path:
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if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb))
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goto csum_error;
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/*
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* RFC1323: H1. Apply PAWS check first.
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*/
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if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
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tcp_paws_discard(sk, skb)) {
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if (!th->rst) {
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NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
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tcp_send_dupack(sk, skb);
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goto discard;
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}
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/* Resets are accepted even if PAWS failed.
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ts_recent update must be made after we are sure
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that the packet is in window.
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*/
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}
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/*
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* Standard slow path.
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*/
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if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
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/* RFC793, page 37: "In all states except SYN-SENT, all reset
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* (RST) segments are validated by checking their SEQ-fields."
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* And page 69: "If an incoming segment is not acceptable,
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* an acknowledgment should be sent in reply (unless the RST bit
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* is set, if so drop the segment and return)".
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*/
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if (!th->rst)
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tcp_send_dupack(sk, skb);
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goto discard;
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}
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if (th->rst) {
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tcp_reset(sk);
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goto discard;
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}
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tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
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if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
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TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
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NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN);
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tcp_reset(sk);
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return 1;
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}
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res = tcp_validate_incoming(sk, skb, th, 1);
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if (res <= 0)
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return -res;
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step5:
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if (th->ack)
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@ -5225,6 +5248,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
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struct tcp_sock *tp = tcp_sk(sk);
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struct inet_connection_sock *icsk = inet_csk(sk);
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int queued = 0;
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int res;
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tp->rx_opt.saw_tstamp = 0;
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@ -5277,42 +5301,9 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
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return 0;
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}
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if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
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tcp_paws_discard(sk, skb)) {
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if (!th->rst) {
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NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
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tcp_send_dupack(sk, skb);
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goto discard;
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}
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/* Reset is accepted even if it did not pass PAWS. */
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}
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/* step 1: check sequence number */
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if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
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if (!th->rst)
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tcp_send_dupack(sk, skb);
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goto discard;
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}
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/* step 2: check RST bit */
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if (th->rst) {
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tcp_reset(sk);
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goto discard;
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}
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tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
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/* step 3: check security and precedence [ignored] */
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/* step 4:
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*
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* Check for a SYN in window.
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*/
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if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
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NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN);
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tcp_reset(sk);
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return 1;
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}
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res = tcp_validate_incoming(sk, skb, th, 0);
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if (res <= 0)
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return -res;
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/* step 5: check the ACK field */
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if (th->ack) {
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