1 files changed, 175 insertions, 43 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index f501ac048366..a7ef679dd3ea 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -866,7 +866,7 @@ 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) ||
+        if (!tp->retransmit_skb_hint ||
             before(TCP_SKB_CB(skb)->seq,
                    TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
                 tp->retransmit_skb_hint = skb;
@@ -1256,7 +1256,7 @@ static u8 tcp_sacktag_one(struct sock *sk,
                 fack_count += pcount;
 
                 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
-                if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) &&
+                if (!tcp_is_fack(tp) && tp->lost_skb_hint &&
                     before(start_seq, TCP_SKB_CB(tp->lost_skb_hint)->seq))
                         tp->lost_cnt_hint += pcount;
 
@@ -1535,7 +1535,7 @@ static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
                 if (!before(TCP_SKB_CB(skb)->seq, end_seq))
                         break;
 
-                if ((next_dup != NULL) &&
+                if (next_dup  &&
                     before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) {
                         in_sack = tcp_match_skb_to_sack(sk, skb,
                                                         next_dup->start_seq,
@@ -1551,7 +1551,7 @@ static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
                 if (in_sack <= 0) {
                         tmp = tcp_shift_skb_data(sk, skb, state,
                                                  start_seq, end_seq, dup_sack);
-                        if (tmp != NULL) {
+                        if (tmp) {
                                 if (tmp != skb) {
                                         skb = tmp;
                                         continue;
@@ -1614,7 +1614,7 @@ static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb,
                                                 struct tcp_sacktag_state *state,
                                                 u32 skip_to_seq)
 {
-        if (next_dup == NULL)
+        if (!next_dup)
                 return skb;
 
         if (before(next_dup->start_seq, skip_to_seq)) {
@@ -1783,7 +1783,7 @@ tcp_sacktag_write_queue(struct sock *sk, const struct sk_buff *ack_skb,
                         if (tcp_highest_sack_seq(tp) == cache->end_seq) {
                                 /* ...but better entrypoint exists! */
                                 skb = tcp_highest_sack(sk);
-                                if (skb == NULL)
+                                if (!skb)
                                         break;
                                 state.fack_count = tp->fackets_out;
                                 cache++;
@@ -1798,7 +1798,7 @@ tcp_sacktag_write_queue(struct sock *sk, const struct sk_buff *ack_skb,
 
                 if (!before(start_seq, tcp_highest_sack_seq(tp))) {
                         skb = tcp_highest_sack(sk);
-                        if (skb == NULL)
+                        if (!skb)
                                 break;
                         state.fack_count = tp->fackets_out;
                 }
@@ -3099,17 +3099,15 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
                         if (sacked & TCPCB_SACKED_RETRANS)
                                 tp->retrans_out -= acked_pcount;
                         flag |= FLAG_RETRANS_DATA_ACKED;
-                } else {
+                } else if (!(sacked & TCPCB_SACKED_ACKED)) {
                         last_ackt = skb->skb_mstamp;
                         WARN_ON_ONCE(last_ackt.v64 == 0);
                         if (!first_ackt.v64)
                                 first_ackt = last_ackt;
 
-                        if (!(sacked & TCPCB_SACKED_ACKED)) {
-                                reord = min(pkts_acked, reord);
-                                if (!after(scb->end_seq, tp->high_seq))
-                                        flag |= FLAG_ORIG_SACK_ACKED;
-                        }
+                        reord = min(pkts_acked, reord);
+                        if (!after(scb->end_seq, tp->high_seq))
+                                flag |= FLAG_ORIG_SACK_ACKED;
                 }
 
                 if (sacked & TCPCB_SACKED_ACKED)
@@ -3322,6 +3320,36 @@ static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32
         return flag;
 }
 
+/* Return true if we're currently rate-limiting out-of-window ACKs and
+ * thus shouldn't send a dupack right now. We rate-limit dupacks in
+ * response to out-of-window SYNs or ACKs to mitigate ACK loops or DoS
+ * attacks that send repeated SYNs or ACKs for the same connection. To
+ * do this, we do not send a duplicate SYNACK or ACK if the remote
+ * endpoint is sending out-of-window SYNs or pure ACKs at a high rate.
+ */
+bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
+                          int mib_idx, u32 *last_oow_ack_time)
+{
+        /* Data packets without SYNs are not likely part of an ACK loop. */
+        if ((TCP_SKB_CB(skb)->seq != TCP_SKB_CB(skb)->end_seq) &&
+            !tcp_hdr(skb)->syn)
+                goto not_rate_limited;
+
+        if (*last_oow_ack_time) {
+                s32 elapsed = (s32)(tcp_time_stamp - *last_oow_ack_time);
+
+                if (0 <= elapsed && elapsed < sysctl_tcp_invalid_ratelimit) {
+                        NET_INC_STATS_BH(net, mib_idx);
+                        return true;    /* rate-limited: don't send yet! */
+                }
+        }
+
+        *last_oow_ack_time = tcp_time_stamp;
+
+not_rate_limited:
+        return false;   /* not rate-limited: go ahead, send dupack now! */
+}
+
 /* RFC 5961 7 [ACK Throttling] */
 static void tcp_send_challenge_ack(struct sock *sk, const struct sk_buff *skb)
 {
@@ -3573,6 +3601,23 @@ old_ack:
         return 0;
 }
 
+static void tcp_parse_fastopen_option(int len, const unsigned char *cookie,
+                                      bool syn, struct tcp_fastopen_cookie *foc,
+                                      bool exp_opt)
+{
+        /* Valid only in SYN or SYN-ACK with an even length.  */
+        if (!foc || !syn || len < 0 || (len & 1))
+                return;
+
+        if (len >= TCP_FASTOPEN_COOKIE_MIN &&
+            len <= TCP_FASTOPEN_COOKIE_MAX)
+                memcpy(foc->val, cookie, len);
+        else if (len != 0)
+                len = -1;
+        foc->len = len;
+        foc->exp = exp_opt;
+}
+
 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
  * But, this can also be called on packets in the established flow when
  * the fast version below fails.
@@ -3662,21 +3707,22 @@ void tcp_parse_options(const struct sk_buff *skb,
                                  */
                                 break;
 #endif
+                        case TCPOPT_FASTOPEN:
+                                tcp_parse_fastopen_option(
+                                        opsize - TCPOLEN_FASTOPEN_BASE,
+                                        ptr, th->syn, foc, false);
+                                break;
+
                         case TCPOPT_EXP:
                                 /* Fast Open option shares code 254 using a
-                                 * 16 bits magic number. It's valid only in
-                                 * SYN or SYN-ACK with an even size.
+                                 * 16 bits magic number.
                                  */
-                                if (opsize < TCPOLEN_EXP_FASTOPEN_BASE ||
-                                    get_unaligned_be16(ptr) != TCPOPT_FASTOPEN_MAGIC ||
-                                    foc == NULL || !th->syn || (opsize & 1))
-                                        break;
-                                foc->len = opsize - TCPOLEN_EXP_FASTOPEN_BASE;
-                                if (foc->len >= TCP_FASTOPEN_COOKIE_MIN &&
-                                    foc->len <= TCP_FASTOPEN_COOKIE_MAX)
-                                        memcpy(foc->val, ptr + 2, foc->len);
-                                else if (foc->len != 0)
-                                        foc->len = -1;
+                                if (opsize >= TCPOLEN_EXP_FASTOPEN_BASE &&
+                                    get_unaligned_be16(ptr) ==
+                                    TCPOPT_FASTOPEN_MAGIC)
+                                        tcp_parse_fastopen_option(opsize -
+                                                TCPOLEN_EXP_FASTOPEN_BASE,
+                                                ptr + 2, th->syn, foc, true);
                                 break;
 
                         }
@@ -4640,7 +4686,7 @@ static void tcp_collapse_ofo_queue(struct sock *sk)
         struct sk_buff *head;
         u32 start, end;
 
-        if (skb == NULL)
+        if (!skb)
                 return;
 
         start = TCP_SKB_CB(skb)->seq;
@@ -5095,7 +5141,7 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
 {
         struct tcp_sock *tp = tcp_sk(sk);
 
-        if (unlikely(sk->sk_rx_dst == NULL))
+        if (unlikely(!sk->sk_rx_dst))
                 inet_csk(sk)->icsk_af_ops->sk_rx_dst_set(sk, skb);
         /*
          *      Header prediction.
@@ -5292,7 +5338,7 @@ void tcp_finish_connect(struct sock *sk, struct sk_buff *skb)
 
         tcp_set_state(sk, TCP_ESTABLISHED);
 
-        if (skb != NULL) {
+        if (skb) {
                 icsk->icsk_af_ops->sk_rx_dst_set(sk, skb);
                 security_inet_conn_established(sk, skb);
         }
@@ -5330,8 +5376,8 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
 {
         struct tcp_sock *tp = tcp_sk(sk);
         struct sk_buff *data = tp->syn_data ? tcp_write_queue_head(sk) : NULL;
-        u16 mss = tp->rx_opt.mss_clamp;
-        bool syn_drop;
+        u16 mss = tp->rx_opt.mss_clamp, try_exp = 0;
+        bool syn_drop = false;
 
         if (mss == tp->rx_opt.user_mss) {
                 struct tcp_options_received opt;
@@ -5343,16 +5389,25 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
                 mss = opt.mss_clamp;
         }
 
-        if (!tp->syn_fastopen)  /* Ignore an unsolicited cookie */
+        if (!tp->syn_fastopen) {
+                /* Ignore an unsolicited cookie */
                 cookie->len = -1;
+        } else if (tp->total_retrans) {
+                /* SYN timed out and the SYN-ACK neither has a cookie nor
+                 * acknowledges data. Presumably the remote received only
+                 * the retransmitted (regular) SYNs: either the original
+                 * SYN-data or the corresponding SYN-ACK was dropped.
+                 */
+                syn_drop = (cookie->len < 0 && data);
+        } else if (cookie->len < 0 && !tp->syn_data) {
+                /* We requested a cookie but didn't get it. If we did not use
+                 * the (old) exp opt format then try so next time (try_exp=1).
+                 * Otherwise we go back to use the RFC7413 opt (try_exp=2).
+                 */
+                try_exp = tp->syn_fastopen_exp ? 2 : 1;
+        }
 
-        /* The SYN-ACK neither has cookie nor acknowledges the data. Presumably
-         * the remote receives only the retransmitted (regular) SYNs: either
-         * the original SYN-data or the corresponding SYN-ACK is lost.
-         */
-        syn_drop = (cookie->len <= 0 && data && tp->total_retrans);
-
-        tcp_fastopen_cache_set(sk, mss, cookie, syn_drop);
+        tcp_fastopen_cache_set(sk, mss, cookie, syn_drop, try_exp);
 
         if (data) { /* Retransmit unacked data in SYN */
                 tcp_for_write_queue_from(data, sk) {
@@ -5661,11 +5716,11 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
         }
 
         req = tp->fastopen_rsk;
-        if (req != NULL) {
+        if (req) {
                 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&
                     sk->sk_state != TCP_FIN_WAIT1);
 
-                if (tcp_check_req(sk, skb, req, NULL, true) == NULL)
+                if (!tcp_check_req(sk, skb, req, true))
                         goto discard;
         }
 
@@ -5751,7 +5806,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
                  * ACK we have received, this would have acknowledged
                  * our SYNACK so stop the SYNACK timer.
                  */
-                if (req != NULL) {
+                if (req) {
                         /* Return RST if ack_seq is invalid.
                          * Note that RFC793 only says to generate a
                          * DUPACK for it but for TCP Fast Open it seems
@@ -5913,6 +5968,80 @@ static void tcp_ecn_create_request(struct request_sock *req,
                 inet_rsk(req)->ecn_ok = 1;
 }
 
+static void tcp_openreq_init(struct request_sock *req,
+                             const struct tcp_options_received *rx_opt,
+                             struct sk_buff *skb, const struct sock *sk)
+{
+        struct inet_request_sock *ireq = inet_rsk(req);
+
+        req->rcv_wnd = 0;               /* So that tcp_send_synack() knows! */
+        req->cookie_ts = 0;
+        tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
+        tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
+        tcp_rsk(req)->snt_synack = tcp_time_stamp;
+        tcp_rsk(req)->last_oow_ack_time = 0;
+        req->mss = rx_opt->mss_clamp;
+        req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
+        ireq->tstamp_ok = rx_opt->tstamp_ok;
+        ireq->sack_ok = rx_opt->sack_ok;
+        ireq->snd_wscale = rx_opt->snd_wscale;
+        ireq->wscale_ok = rx_opt->wscale_ok;
+        ireq->acked = 0;
+        ireq->ecn_ok = 0;
+        ireq->ir_rmt_port = tcp_hdr(skb)->source;
+        ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
+        ireq->ir_mark = inet_request_mark(sk, skb);
+}
+
+struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops,
+                                      struct sock *sk_listener)
+{
+        struct request_sock *req = reqsk_alloc(ops, sk_listener);
+
+        if (req) {
+                struct inet_request_sock *ireq = inet_rsk(req);
+
+                kmemcheck_annotate_bitfield(ireq, flags);
+                ireq->opt = NULL;
+                atomic64_set(&ireq->ir_cookie, 0);
+                ireq->ireq_state = TCP_NEW_SYN_RECV;
+                write_pnet(&ireq->ireq_net, sock_net(sk_listener));
+                ireq->ireq_family = sk_listener->sk_family;
+        }
+
+        return req;
+}
+EXPORT_SYMBOL(inet_reqsk_alloc);
+
+/*
+ * Return true if a syncookie should be sent
+ */
+static bool tcp_syn_flood_action(struct sock *sk,
+                                 const struct sk_buff *skb,
+                                 const char *proto)
+{
+        const char *msg = "Dropping request";
+        bool want_cookie = false;
+        struct listen_sock *lopt;
+
+#ifdef CONFIG_SYN_COOKIES
+        if (sysctl_tcp_syncookies) {
+                msg = "Sending cookies";
+                want_cookie = true;
+                NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPREQQFULLDOCOOKIES);
+        } else
+#endif
+                NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPREQQFULLDROP);
+
+        lopt = inet_csk(sk)->icsk_accept_queue.listen_opt;
+        if (!lopt->synflood_warned && sysctl_tcp_syncookies != 2) {
+                lopt->synflood_warned = 1;
+                pr_info("%s: Possible SYN flooding on port %d. %s.  Check SNMP counters.\n",
+                        proto, ntohs(tcp_hdr(skb)->dest), msg);
+        }
+        return want_cookie;
+}
+
 int tcp_conn_request(struct request_sock_ops *rsk_ops,
                      const struct tcp_request_sock_ops *af_ops,
                      struct sock *sk, struct sk_buff *skb)
@@ -5950,7 +6079,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
                 goto drop;
         }
 
-        req = inet_reqsk_alloc(rsk_ops);
+        req = inet_reqsk_alloc(rsk_ops, sk);
         if (!req)
                 goto drop;
 
@@ -5967,6 +6096,9 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
         tmp_opt.tstamp_ok = tmp_opt.saw_tstamp;
         tcp_openreq_init(req, &tmp_opt, skb, sk);
 
+        /* Note: tcp_v6_init_req() might override ir_iif for link locals */
+        inet_rsk(req)->ir_iif = sk->sk_bound_dev_if;
+
         af_ops->init_req(req, sk, skb);
 
         if (security_inet_conn_request(sk, skb, req))
@@ -6039,7 +6171,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
                 if (err || want_cookie)
                         goto drop_and_free;
 
-                tcp_rsk(req)->listener = NULL;
+                tcp_rsk(req)->tfo_listener = false;
                 af_ops->queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
         }