tcp: export count for rehash attempts

Using IPv6 flow-label to swiftly route around avoid congested or
disconnected network path can greatly improve TCP reliability.

This patch adds SNMP counters and a OPT_STATS counter to track both
host-level and connection-level statistics. Network administrators
can use these counters to evaluate the impact of this new ability better.

Export count for rehash attempts to
1) two SNMP counters: TcpTimeoutRehash (rehash due to timeouts),
   and TcpDuplicateDataRehash (rehash due to receiving duplicate
   packets)
2) Timestamping API SOF_TIMESTAMPING_OPT_STATS.

Signed-off-by: Abdul Kabbani <akabbani@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Kevin(Yudong) Yang <yyd@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 4e2124607d325c54f572ce62c1e70581da6b0a72..1cf73e6f85ca8358574762088ed216cf38b73cb6 100644 (file)
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -386,6 +386,8 @@ struct tcp_sock {
 #define BPF_SOCK_OPS_TEST_FLAG(TP, ARG) 0
 #endif
 
+       u16 timeout_rehash;     /* Timeout-triggered rehash attempts */
+
        u32 rcv_ooopack; /* Received out-of-order packets, for tcpinfo */
 
 /* Receiver side RTT estimation */

diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 7eee233e78d2740e15b2abe445f7b6d40d217846..7d91f4debc483f28632b9070be231331ffc51ed6 100644 (file)
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -285,6 +285,8 @@ enum
        LINUX_MIB_TCPRCVQDROP,                  /* TCPRcvQDrop */
        LINUX_MIB_TCPWQUEUETOOBIG,              /* TCPWqueueTooBig */
        LINUX_MIB_TCPFASTOPENPASSIVEALTKEY,     /* TCPFastOpenPassiveAltKey */
+       LINUX_MIB_TCPTIMEOUTREHASH,             /* TCPTimeoutRehash */
+       LINUX_MIB_TCPDUPLICATEDATAREHASH,       /* TCPDuplicateDataRehash */
        __LINUX_MIB_MAX
 };
 

diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index d87184e673ca8341fb09c289ade5fc00c57f6c35..fd9eb8f6bcae37cb7eeafea8d3122b9afd630032 100644 (file)
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -311,6 +311,7 @@ enum {
        TCP_NLA_DSACK_DUPS,     /* DSACK blocks received */
        TCP_NLA_REORD_SEEN,     /* reordering events seen */
        TCP_NLA_SRTT,           /* smoothed RTT in usecs */
+       TCP_NLA_TIMEOUT_REHASH, /* Timeout-triggered rehash attempts */
 };
 
 /* for TCP_MD5SIG socket option */

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index cc90243ccf767807cad7fa47ba808df75554fd5e..2580303249e23e64ec94afc79cdeb7d31a492612 100644 (file)
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -289,6 +289,8 @@ static const struct snmp_mib snmp4_net_list[] = {
        SNMP_MIB_ITEM("TCPRcvQDrop", LINUX_MIB_TCPRCVQDROP),
        SNMP_MIB_ITEM("TCPWqueueTooBig", LINUX_MIB_TCPWQUEUETOOBIG),
        SNMP_MIB_ITEM("TCPFastOpenPassiveAltKey", LINUX_MIB_TCPFASTOPENPASSIVEALTKEY),
+       SNMP_MIB_ITEM("TcpTimeoutRehash", LINUX_MIB_TCPTIMEOUTREHASH),
+       SNMP_MIB_ITEM("TcpDuplicateDataRehash", LINUX_MIB_TCPDUPLICATEDATAREHASH),
        SNMP_MIB_SENTINEL
 };
 

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 2857c853e2fdc6ffcd2e07db34c3a213c3315de7..484485ae74c26eb43d49d972e068bcf5d0e33d58 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3337,6 +3337,7 @@ static size_t tcp_opt_stats_get_size(void)
                nla_total_size(sizeof(u32)) + /* TCP_NLA_DSACK_DUPS */
                nla_total_size(sizeof(u32)) + /* TCP_NLA_REORD_SEEN */
                nla_total_size(sizeof(u32)) + /* TCP_NLA_SRTT */
+               nla_total_size(sizeof(u16)) + /* TCP_NLA_TIMEOUT_REHASH */
                0;
 }
 
@@ -3391,6 +3392,7 @@ struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk)
        nla_put_u32(stats, TCP_NLA_DSACK_DUPS, tp->dsack_dups);
        nla_put_u32(stats, TCP_NLA_REORD_SEEN, tp->reord_seen);
        nla_put_u32(stats, TCP_NLA_SRTT, tp->srtt_us >> 3);
+       nla_put_u16(stats, TCP_NLA_TIMEOUT_REHASH, tp->timeout_rehash);
 
        return stats;
 }

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 4915de65d278df22f04338f26ad364ae607358dc..e8b840a4767e140dc8a82ceebb0774b5402dfe4e 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4271,8 +4271,10 @@ static void tcp_rcv_spurious_retrans(struct sock *sk, const struct sk_buff *skb)
         * The receiver remembers and reflects via DSACKs. Leverage the
         * DSACK state and change the txhash to re-route speculatively.
         */
-       if (TCP_SKB_CB(skb)->seq == tcp_sk(sk)->duplicate_sack[0].start_seq)
+       if (TCP_SKB_CB(skb)->seq == tcp_sk(sk)->duplicate_sack[0].start_seq) {
                sk_rethink_txhash(sk);
+               NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDUPLICATEDATAREHASH);
+       }
 }
 
 static void tcp_send_dupack(struct sock *sk, const struct sk_buff *skb)

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 1097b438befe14ae3f375f3dbcc1f2d375a93879..c3f26dcd6704ee6b160c7a59667f82bc940f8cbe 100644 (file)
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -223,6 +223,9 @@ static int tcp_write_timeout(struct sock *sk)
                        dst_negative_advice(sk);
                } else {
                        sk_rethink_txhash(sk);
+                       tp->timeout_rehash++;
+                       __NET_INC_STATS(sock_net(sk),
+                                       LINUX_MIB_TCPTIMEOUTREHASH);
                }
                retry_until = icsk->icsk_syn_retries ? : net->ipv4.sysctl_tcp_syn_retries;
                expired = icsk->icsk_retransmits >= retry_until;
@@ -234,6 +237,9 @@ static int tcp_write_timeout(struct sock *sk)
                        dst_negative_advice(sk);
                } else {
                        sk_rethink_txhash(sk);
+                       tp->timeout_rehash++;
+                       __NET_INC_STATS(sock_net(sk),
+                                       LINUX_MIB_TCPTIMEOUTREHASH);
                }
 
                retry_until = net->ipv4.sysctl_tcp_retries2;