>
https://bugzilla.kernel.org/show_bug.cgi?id=18952
>
> Summary: The mount of SYN retries is not equal to
> /proc/sys/net/ipv4/tcp_syn_retries
> Product: Networking
> Version: 2.5
> Kernel Version: 2.6.32.12, 2.6.32.15, 2.6.35.4
> Platform: All
> OS/Version: Linux
> Tree: Mainline
> Status: NEW
> Severity: normal
> Priority: P1
> Component: IPV4
> AssignedTo:
shemminger@linux-foundation.org
> ReportedBy:
yuri@itinteg.net
> Regression: No
>
>
> When setting a value in /proc/sys/net/ipv4/tcp_syn_retries, the actual number
> of syn retries is the number set in /proc/sys/net/ipv4/tcp_syn_retries minus
> 2.
>
> For example:
> When setting /proc/sys/net/ipv4/tcp_syn_retries to 5 the actual number of SYN
> retries is 3.
> When setting /proc/sys/net/ipv4/tcp_syn_retries to 7 the actual number of SYN
> retries is 5.
> However, when setting setting /proc/sys/net/ipv4/tcp_syn_retries to 2 the
> actual number of SYN retries is 2.
>
> Note: In the kernel 2.6.31.9 actual number of SYN = tcp_syn_retries + 1
>
>
> Steps to reproduce:
> sudo iptables -I INPUT 1 -i lo -p tcp --dport 88 -j DROP
> sudo tcpdump -n -i lo -v tcp port 88
>
> from another console run:
> time wget -t 1 -O - --connect-timeout=300
http://0:88
>
> tcpdump output:
> sudo tcpdump -n -i lo -v tcp port 88
> 11:29:39.820058 IP (tos 0x0, ttl 64, id 14664, offset 0, flags [DF], proto TCP
> (6), length 60)
> 127.0.0.1.43730 > 127.0.0.1.kerberos: Flags [S], cksum 0xfe30 (incorrect ->
> 0xecf4), seq 1012617667, win 32792, options [mss 16396,sackOK,TS val 12871819
> ecr 0,nop,wscale 7], length 0
> 11:29:42.824091 IP (tos 0x0, ttl 64, id 14665, offset 0, flags [DF], proto TCP
> (6), length 60)
> 127.0.0.1.43730 > 127.0.0.1.kerberos: Flags [S], cksum 0xfe30 (incorrect ->
> 0xe137), seq 1012617667, win 32792, options [mss 16396,sackOK,TS val 12874824
> ecr 0,nop,wscale 7], length 0
> 11:29:48.832153 IP (tos 0x0, ttl 64, id 14666, offset 0, flags [DF], proto TCP
> (6), length 60)
> 127.0.0.1.43730 > 127.0.0.1.kerberos: Flags [S], cksum 0xfe30 (incorrect ->
> 0xc9bf), seq 1012617667, win 32792, options [mss 16396,sackOK,TS val 12880832
> ecr 0,nop,wscale 7], length 0
>
> wget output:
> time wget -t 1 -O - --connect-timeout=300
http://0:88
> Resolving 0... 0.0.0.0
> Connecting to 0|0.0.0.0|:88... failed: Connection timed out.
> Giving up.
>
>
> real 0m21.050s
> user 0m0.003s
> sys 0m0.004s
>
> It valid for remote host also.
>
