 | | | RHEL dropping tcp connections | RHEL dropping tcp connections 2005-01-13 - By Figueiredo, Charles
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Hello,
I'm running systems patched to Update 3, but with the Update 4
kernel loaded to work-around some kswapd issues we've run into on
heavily-loaded systems.
We have one particular host that drops tcp connections on a
regular basis. I've noticed this with both ssh sessions and sqsh
connections to db systems. There have even been cases where netstat
reports that connections are "established", but when I check the other
servers they show no connection from the host.
I have verified the hardware aspect: this isn't a duplexity
issue, and the switch or netstat -i shows absolutely no frame errors.
The problem doesn't seem to be layer 2.
Has anyone experienced this or have any insight here?
I'll include some data (netstat -i, sysctl -a | grep net,
netstat -s) in case anyone can find anything in it:
Thanks,
-charles.
==========
netstat -i
==========
Kernel Interface table
Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP
TX-OVR Flg
eth0 1500 0 15493153 0 0 0 13612049 0 0
0 BMRU
lo 16436 0 52382424 0 0 0 52382424 0 0
0 LRU
====================
Sysctl -a | grep net
====================
net.unix.max_dgram_qlen = 10
net.token-ring.rif_timeout = 60000
net.ipv4.conf.eth0.force_igmp_version = 0
net.ipv4.conf.eth0.disable_policy = 0
net.ipv4.conf.eth0.disable_xfrm = 0
net.ipv4.conf.eth0.arp_filter = 0
net.ipv4.conf.eth0.tag = 0
net.ipv4.conf.eth0.log_martians = 0
net.ipv4.conf.eth0.bootp_relay = 0
net.ipv4.conf.eth0.medium_id = 0
net.ipv4.conf.eth0.proxy_arp = 0
net.ipv4.conf.eth0.accept_source_route = 1
net.ipv4.conf.eth0.send_redirects = 1
net.ipv4.conf.eth0.rp_filter = 1
net.ipv4.conf.eth0.shared_media = 1
net.ipv4.conf.eth0.secure_redirects = 1
net.ipv4.conf.eth0.accept_redirects = 1
net.ipv4.conf.eth0.mc_forwarding = 0
net.ipv4.conf.eth0.forwarding = 0
net.ipv4.conf.lo.force_igmp_version = 0
net.ipv4.conf.lo.disable_policy = 0
net.ipv4.conf.lo.disable_xfrm = 0
net.ipv4.conf.lo.arp_filter = 0
net.ipv4.conf.lo.tag = 0
net.ipv4.conf.lo.log_martians = 0
net.ipv4.conf.lo.bootp_relay = 0
net.ipv4.conf.lo.medium_id = 0
net.ipv4.conf.lo.proxy_arp = 0
net.ipv4.conf.lo.accept_source_route = 1
net.ipv4.conf.lo.send_redirects = 1
net.ipv4.conf.lo.rp_filter = 1
net.ipv4.conf.lo.shared_media = 1
net.ipv4.conf.lo.secure_redirects = 1
net.ipv4.conf.lo.accept_redirects = 1
net.ipv4.conf.lo.mc_forwarding = 0
net.ipv4.conf.lo.forwarding = 0
net.ipv4.conf.default.force_igmp_version = 0
net.ipv4.conf.default.disable_policy = 0
net.ipv4.conf.default.disable_xfrm = 0
net.ipv4.conf.default.arp_filter = 0
net.ipv4.conf.default.tag = 0
net.ipv4.conf.default.log_martians = 0
net.ipv4.conf.default.bootp_relay = 0
net.ipv4.conf.default.medium_id = 0
net.ipv4.conf.default.proxy_arp = 0
net.ipv4.conf.default.accept_source_route = 1
net.ipv4.conf.default.send_redirects = 1
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.default.shared_media = 1
net.ipv4.conf.default.secure_redirects = 1
net.ipv4.conf.default.accept_redirects = 1
net.ipv4.conf.default.mc_forwarding = 0
net.ipv4.conf.default.forwarding = 0
net.ipv4.conf.all.force_igmp_version = 0
net.ipv4.conf.all.disable_policy = 0
net.ipv4.conf.all.disable_xfrm = 0
net.ipv4.conf.all.arp_filter = 0
net.ipv4.conf.all.tag = 0
net.ipv4.conf.all.log_martians = 0
net.ipv4.conf.all.bootp_relay = 0
net.ipv4.conf.all.medium_id = 0
net.ipv4.conf.all.proxy_arp = 0
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.all.send_redirects = 1
net.ipv4.conf.all.rp_filter = 0
net.ipv4.conf.all.shared_media = 1
net.ipv4.conf.all.secure_redirects = 1
net.ipv4.conf.all.accept_redirects = 1
net.ipv4.conf.all.mc_forwarding = 0
net.ipv4.conf.all.forwarding = 0
net.ipv4.neigh.eth0.locktime = 100
net.ipv4.neigh.eth0.proxy_delay = 80
net.ipv4.neigh.eth0.anycast_delay = 100
net.ipv4.neigh.eth0.proxy_qlen = 64
net.ipv4.neigh.eth0.unres_qlen = 3
net.ipv4.neigh.eth0.gc_stale_time = 60
net.ipv4.neigh.eth0.delay_first_probe_time = 5
net.ipv4.neigh.eth0.base_reachable_time = 30
net.ipv4.neigh.eth0.retrans_time = 100
net.ipv4.neigh.eth0.app_solicit = 0
net.ipv4.neigh.eth0.ucast_solicit = 3
net.ipv4.neigh.eth0.mcast_solicit = 3
net.ipv4.neigh.lo.locktime = 100
net.ipv4.neigh.lo.proxy_delay = 80
net.ipv4.neigh.lo.anycast_delay = 100
net.ipv4.neigh.lo.proxy_qlen = 64
net.ipv4.neigh.lo.unres_qlen = 3
net.ipv4.neigh.lo.gc_stale_time = 60
net.ipv4.neigh.lo.delay_first_probe_time = 5
net.ipv4.neigh.lo.base_reachable_time = 30
net.ipv4.neigh.lo.retrans_time = 100
net.ipv4.neigh.lo.app_solicit = 0
net.ipv4.neigh.lo.ucast_solicit = 3
net.ipv4.neigh.lo.mcast_solicit = 3
net.ipv4.neigh.default.gc_thresh3 = 1024
net.ipv4.neigh.default.gc_thresh2 = 512
net.ipv4.neigh.default.gc_thresh1 = 128
net.ipv4.neigh.default.gc_interval = 30
net.ipv4.neigh.default.locktime = 100
net.ipv4.neigh.default.proxy_delay = 80
net.ipv4.neigh.default.anycast_delay = 100
net.ipv4.neigh.default.proxy_qlen = 64
net.ipv4.neigh.default.unres_qlen = 3
net.ipv4.neigh.default.gc_stale_time = 60
net.ipv4.neigh.default.delay_first_probe_time = 5
net.ipv4.neigh.default.base_reachable_time = 30
net.ipv4.neigh.default.retrans_time = 100
net.ipv4.neigh.default.app_solicit = 0
net.ipv4.neigh.default.ucast_solicit = 3
net.ipv4.neigh.default.mcast_solicit = 3
net.ipv4.ipfrag_secret_interval = 600
net.ipv4.tcp_low_latency = 0
net.ipv4.tcp_frto = 0
net.ipv4.tcp_tw_reuse = 0
net.ipv4.icmp_ratemask = 6168
net.ipv4.icmp_ratelimit = 100
net.ipv4.tcp_adv_win_scale = 2
net.ipv4.tcp_app_win = 31
net.ipv4.tcp_rmem = 4096 87380 174760
net.ipv4.tcp_wmem = 4096 16384 131072
net.ipv4.tcp_mem = 195584 196096 196608
net.ipv4.tcp_dsack = 1
net.ipv4.tcp_ecn = 0
net.ipv4.tcp_reordering = 3
net.ipv4.tcp_fack = 1
net.ipv4.tcp_orphan_retries = 0
net.ipv4.inet_peer_gc_maxtime = 120
net.ipv4.inet_peer_gc_mintime = 10
net.ipv4.inet_peer_maxttl = 600
net.ipv4.inet_peer_minttl = 120
net.ipv4.inet_peer_threshold = 65664
net.ipv4.igmp_max_memberships = 20
net.ipv4.route.secret_interval = 600
net.ipv4.route.min_adv_mss = 256
net.ipv4.route.min_pmtu = 552
net.ipv4.route.mtu_expires = 600
net.ipv4.route.gc_elasticity = 8
net.ipv4.route.error_burst = 500
net.ipv4.route.error_cost = 100
net.ipv4.route.redirect_silence = 2048
net.ipv4.route.redirect_number = 9
net.ipv4.route.redirect_load = 2
net.ipv4.route.gc_interval = 60
net.ipv4.route.gc_timeout = 300
net.ipv4.route.gc_min_interval = 0
net.ipv4.route.max_size = 1048576
net.ipv4.route.gc_thresh = 65536
net.ipv4.route.max_delay = 10
net.ipv4.route.min_delay = 2
net.ipv4.icmp_ignore_bogus_error_responses = 0
net.ipv4.icmp_echo_ignore_broadcasts = 0
net.ipv4.icmp_echo_ignore_all = 0
net.ipv4.ip_local_port_range = 32768 61000
net.ipv4.tcp_max_syn_backlog = 1024
net.ipv4.tcp_rfc1337 = 0
net.ipv4.tcp_stdurg = 0
net.ipv4.tcp_abort_on_overflow = 0
net.ipv4.tcp_tw_recycle = 0
net.ipv4.tcp_syncookies = 0
net.ipv4.tcp_fin_timeout = 60
net.ipv4.tcp_retries2 = 15
net.ipv4.tcp_retries1 = 3
net.ipv4.tcp_keepalive_intvl = 75
net.ipv4.tcp_keepalive_probes = 9
net.ipv4.tcp_keepalive_time = 7200
net.ipv4.ipfrag_time = 30
net.ipv4.ip_dynaddr = 0
net.ipv4.ipfrag_low_thresh = 196608
net.ipv4.ipfrag_high_thresh = 262144
net.ipv4.tcp_max_tw_buckets = 180000
net.ipv4.tcp_max_orphans = 32768
net.ipv4.tcp_synack_retries = 5
net.ipv4.tcp_syn_retries = 5
net.ipv4.ip_nonlocal_bind = 0
net.ipv4.ip_no_pmtu_disc = 0
net.ipv4.ip_autoconfig = 0
net.ipv4.ip_default_ttl = 64
net.ipv4.ip_forward = 0
net.ipv4.tcp_retrans_collapse = 1
net.ipv4.tcp_sack = 1
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_timestamps = 1
net.core.divert_version = 0.46
net.core.hot_list_length = 128
net.core.optmem_max = 10240
net.core.message_burst = 50
net.core.message_cost = 5
net.core.mod_cong = 290
net.core.lo_cong = 100
net.core.no_cong = 20
net.core.no_cong_thresh = 20
net.core.netdev_max_backlog = 300
net.ipv4.route.min_adv_mss = 256
net.ipv4.route.min_pmtu = 552
net.ipv4.route.mtu_expires = 600
net.ipv4.route.gc_elasticity = 8
net.ipv4.route.error_burst = 500
net.ipv4.route.error_cost = 100
net.ipv4.route.redirect_silence = 2048
net.ipv4.route.redirect_number = 9
net.ipv4.route.redirect_load = 2
net.ipv4.route.gc_interval = 60
net.ipv4.route.gc_timeout = 300
net.ipv4.route.gc_min_interval = 0
net.ipv4.route.max_size = 1048576
net.ipv4.route.gc_thresh = 65536
net.ipv4.route.max_delay = 10
net.ipv4.route.min_delay = 2
net.ipv4.icmp_ignore_bogus_error_responses = 0
net.ipv4.icmp_echo_ignore_broadcasts = 0
net.ipv4.icmp_echo_ignore_all = 0
net.ipv4.ip_local_port_range = 32768 61000
net.ipv4.tcp_max_syn_backlog = 1024
net.ipv4.tcp_rfc1337 = 0
net.ipv4.tcp_stdurg = 0
net.ipv4.tcp_abort_on_overflow = 0
net.ipv4.tcp_tw_recycle = 0
net.ipv4.tcp_syncookies = 0
net.ipv4.tcp_fin_timeout = 60
net.ipv4.tcp_retries2 = 15
net.ipv4.tcp_retries1 = 3
net.ipv4.tcp_keepalive_intvl = 75
net.ipv4.tcp_keepalive_probes = 9
net.ipv4.tcp_keepalive_time = 7200
net.ipv4.ipfrag_time = 30
net.ipv4.ip_dynaddr = 0
net.ipv4.ipfrag_low_thresh = 196608
net.ipv4.ipfrag_high_thresh = 262144
net.ipv4.tcp_max_tw_buckets = 180000
net.ipv4.tcp_max_orphans = 32768
net.ipv4.tcp_synack_retries = 5
net.ipv4.tcp_syn_retries = 5
net.ipv4.ip_nonlocal_bind = 0
net.ipv4.ip_no_pmtu_disc = 0
net.ipv4.ip_autoconfig = 0
net.ipv4.ip_default_ttl = 64
net.ipv4.ip_forward = 0
net.ipv4.tcp_retrans_collapse = 1
net.ipv4.tcp_sack = 1
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_timestamps = 1
net.core.divert_version = 0.46
net.core.hot_list_length = 128
net.core.optmem_max = 10240
net.core.message_burst = 50
net.core.message_cost = 5
net.core.mod_cong = 290
net.core.lo_cong = 100
net.core.no_cong = 20
net.core.no_cong_thresh = 20
net.core.netdev_max_backlog = 300
net.core.dev_weight = 64
net.core.rmem_default = 65535
net.core.wmem_default = 65535
net.core.rmem_max = 131071
net.core.wmem_max = 131071
==========
netstat -s
==========
Ip:
65701736 total packets received
0 forwarded
0 incoming packets discarded
65637562 incoming packets delivered
65947395 requests sent out
Icmp:
3367 ICMP messages received
3303 input ICMP message failed.
ICMP input histogram:
destination unreachable: 38
echo requests: 22
echo replies: 5
60 ICMP messages sent
0 ICMP messages failed
ICMP output histogram:
destination unreachable: 38
echo replies: 22
Tcp:
5909 active connections openings
3680 passive connection openings
2 failed connection attempts
205 connection resets received
16 connections established
11404976 segments received
13351070 segments send out
103 segments retransmited
0 bad segments received.
526 resets sent
Udp:
53971161 packets received
10 packets to unknown port received.
0 packet receive errors
52596256 packets sent
TcpExt:
4 resets received for embryonic SYN_RECV sockets
28 packets pruned from receive queue because of socket buffer
overrun
16 ICMP packets dropped because they were out-of-window
ArpFilter: 0
5410 TCP sockets finished time wait in fast timer
40576 delayed acks sent
83 delayed acks further delayed because of locked socket
Quick ack mode was activated 80 times
120884 packets directly queued to recvmsg prequeue.
83571 packets directly received from backlog
13011596 packets directly received from prequeue
6996504 packets header predicted
25431 packets header predicted and directly queued to user
TCPPureAcks: 14859
TCPHPAcks: 5360708
TCPRenoRecovery: 0
TCPSackRecovery: 0
TCPSACKReneging: 0
TCPFACKReorder: 0
TCPSACKReorder: 0
TCPRenoReorder: 0
TCPTSReorder: 0
TCPFullUndo: 0
TCPPartialUndo: 0
TCPDSACKUndo: 0
TCPLossUndo: 3
TCPLoss: 0
TCPLostRetransmit: 0
TCPRenoFailures: 0
TCPSackFailures: 0
TCPLossFailures: 0
TCPFastRetrans: 0
TCPForwardRetrans: 0
TCPSlowStartRetrans: 0
TCPTimeouts: 37
TCPRenoRecoveryFail: 0
TCPSackRecoveryFail: 0
TCPSchedulerFailed: 0
TCPRcvCollapsed: 1747
TCPDSACKOldSent: 80
TCPDSACKOfoSent: 297
TCPDSACKRecv: 0
TCPDSACKOfoRecv: 0
TCPAbortOnSyn: 0
TCPAbortOnData: 4
TCPAbortOnClose: 1
TCPAbortOnMemory: 0
TCPAbortOnTimeout: 2
TCPAbortOnLinger: 0
TCPAbortFailed: 0
TCPMemoryPressures: 0
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