$cat /proc/sys/net/ipv4/tcp_reordering 3 $ tcp_reordering – INTEGER Maximal reordering of packets in a TCP stream. Default: 3 proj-rep/kernel_code/tcp_ipv4.c 1921: tp->reordering = sysctl_tcp_reordering; 1922: nms.csail.mit.edu/~kandula/data/tcp-mult.tgz – Unknown – C irestarter-0.9.0/src/netfilter-script.c 271: fprintf (script, “# Set TCP Re-Ordering value in kernel to ‘5’\n”); 272: fprintf (script, “if [ -e /proc/sys/net/ipv4/tcp_reordering ]; then\n” 273: ” echo 5 > …
Category Archives: Uncategorized
characteristics about the last connection…
$cat /proc/sys/net/ipv4/tcp_no_metrics_save 0 $ tcp_no_metrics_save Normally, TCP will remember some characteristics about the last connection in the flow cache. If tcp_no_metrics_save is set, then it doesn’t. Useful for benchmarks or other tests. net/ipv4/sysctl_net_ipv4.c – 24 identical 452: { 453: .procname = “tcp_no_metrics_save”, 454: .data = &sysctl_tcp_nometrics_save, github.com/github/linux-2.6.git – GPL – C – More from linux-2.6.git …
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controls tcp packetization-layer ..
$cat /proc/sys/net/ipv4/tcp_mtu_probing 0 $ tcp_mtu_probing – INTEGER Controls TCP Packetization-Layer Path MTU Discovery. Takes three values: 0 – Disabled 1 – Disabled by default, enabled when an ICMP black hole detected 2 – Always enabled, use initial MSS of tcp_base_mss. source : Linux kernel Documentation. 2.6.32 147: /* Black hole detection */ 148: tcp_mtu_probing(icsk, sk); …
tcp moderate …receive buffer auto-tuning
$cat /proc/sys/net/ipv4/tcp_moderate_rcvbuf 1 $ tcp_moderate_rcvbuf – BOOLEAN If set, TCP performs receive buffer auto-tuning, attempting to automatically size the buffer (no greater than tcp_rmem[2]) to match the size required by the path for full throughput. Enabled by default. source : Linux kernel Documentation kernel ( 2.6.32 ) trunk/coverage/common/ServerSpecs.pm – 1 identical 278: 247 tcp_max_syn_backlog 1024 …
tcp mem vector of 3 integers
$cat /proc/sys/net/ipv4/tcp_mem 40704 54272 81408 $ tcp_mem vector of 3 INTEGERs: min, pressure, max min: below this number of pages TCP is not bothered about its memory appetite. pressure: when amount of memory allocated by TCP exceeds this number of pages, TCP moderates its memory consumption and enters memory pressure mode, which is exited when …
timewait sockets held…tw_bucket
$cat /proc/sys/net/ipv4/tcp_max_tw_buckets 180000 $ tcp_max_tw_buckets Maximal number of timewait sockets held by system simultaneously. If this number is exceeded time-wait socket is immediately destroyed and warning is printed. This limit exists only to prevent simple DoS attacks, you _must_ not lower the limit artificially, but rather increase it (probably, after increasing installed memory), if network …
grep .. -m .. stop reading a file…
-m Stop reading a file after NUM matching lines. $grep -m 1 wc wcwidth.c #include $grep -m 2 wc wcwidth.c #include wchar_t cr; $grep -m 3 wc wcwidth.c #include wchar_t cr; value=wcwidth(cr); $grep -m 4 wc wcwidth.c #include wchar_t cr; value=wcwidth(cr); $grep -m 0 wc wcwidth.c $ scripts/makelst – 338 identical 19: t1=`$3 –syms $1 …
remembered connection requests .. syn .. backlog
$cat /proc/sys/net/ipv4/tcp_max_syn_backlog 1024 $ Maximal number of remembered connection requests, which still did not receive an acknowledgement from connecting client. The default value is 1024 for systems with more than 128 MB of memory, and 128 for low memory machines. If server suffers of overload, try to increase this number. source : http://www.linuxinsight.com/proc_sys_net_ipv4_tcp_max_syn_backlog.html Script.January/HPUX11/GEN003600 – …
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grep … matches..and that not matches..-l.. -L
$grep -r -l tcp_max * sysctl_net_ipv4.c tcp.c tcp_cong.c tcp_input.c tcp_output.c $ $grep -r -L tcp_max * af_inet.c ah4.c arp.c cipso_ipv4.c datagram.c devinet.c esp4.c fib_frontend.c fib_hash.c fib_lookup.h fib_rules.c fib_semantics.c fib_trie.c icmp.c igmp.c inet_connection_sock.c inet_diag.c inet_fragment.c inet_hashtables.c inet_lro.c inetpeer.c inet_timewait_sock.c ipcomp.c ipconfig.c ip_forward.c ip_fragment.c ip_gre.c ip_input.c ipip.c ipmr.c ip_options.c ip_output.c ip_sockglue.c Kconfig Makefile netfilter/ipt_ECN.c netfilter/nf_nat_amanda.c netfilter/nf_conntrack_l3proto_ipv4.c netfilter/nf_nat_proto_dccp.c …
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The tcp max orphans variable …
$cat /proc/sys/net/ipv4/tcp_max_orphans 8192 $ tcp_max_orphans The tcp_max_orphans variable tells the kernel how many TCP sockets that are not attached to any user file handle to maintain. In case this number is exceeded, orphaned connections are immediately reset and a warning is printed. The only reason for this limit to exist is to prevent some simple …