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Find socket options specified by Linux executable

I need to find out the socket settings that the executing client program set when opening TCP connections on the server. The client runs on Linux. Is it available under /proc/tcp?

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I also had to do this.

lsofdoes not help, since tcp parameters are not displayed in the standard /proc/.

I used this kernel module https://github.com/veithen/knetstat which I modified to work with older versions of the kernel, and also here: https://github.com/abligh/knetstat

This allows:

# cat /proc/net/tcpstat | head
Recv-Q Send-Q Local Address           Foreign Address         Stat Diag Options
     0      0 0.0.0.0:16013           0.0.0.0:*               LSTN      SO_REUSEADDR=0,SO_KEEPALIVE=0,TCP_NODELAY=0
     0      0 127.0.0.1:25            0.0.0.0:*               LSTN      SO_REUSEADDR=1,SO_KEEPALIVE=1,TCP_NODELAY=0
     0      0 0.0.0.0:111             0.0.0.0:*               LSTN      SO_REUSEADDR=1,SO_KEEPALIVE=0,TCP_NODELAY=0
     0      0 0.0.0.0:4643            0.0.0.0:*               LSTN      SO_REUSEADDR=1,SO_KEEPALIVE=0,TCP_NODELAY=0
     0      0 127.0.0.1:753           0.0.0.0:*               LSTN      SO_REUSEADDR=1,SO_KEEPALIVE=0,TCP_NODELAY=0
     0      0 127.0.0.1:113           0.0.0.0:*               LSTN      SO_REUSEADDR=1,SO_KEEPALIVE=0,TCP_NODELAY=0
     0      0 127.0.0.1:754           0.0.0.0:*               LSTN      SO_REUSEADDR=1,SO_KEEPALIVE=0,TCP_NODELAY=0
     0      0 127.0.0.1:1234          0.0.0.0:*               LSTN      SO_REUSEADDR=1,SO_KEEPALIVE=0,TCP_NODELAY=0
     0      0 0.0.0.0:53618           0.0.0.0:*               LSTN      SO_REUSEADDR=0,SO_KEEPALIVE=0,TCP_NODELAY=0
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ltrace, , .

0

lsof -p [PROC_ID] fd . man lsof, . :

[ 11:42 root@hozbox /proc/6828 ]# lsof -p 6828
COMMAND    PID USER   FD   TYPE  DEVICE SIZE/OFF    NODE NAME
SOAnswer_T 6828  jon  cwd    DIR    8,17     4096 3498003 /home/jon/SO/python
SOAnswer_T 6828  jon  rtd    DIR   253,0     4096       2 /
SOAnswer_T 6828  jon  txt    REG   253,0     6088   38614 /usr/bin/python
SOAnswer_T 6828  jon  mem    REG   253,0    20676   16173 /usr/lib/python2.6/lib-dynload/selectmodule.so
SOAnswer_T 6828  jon  mem    REG   253,0    32800   91247 /usr/lib/python2.6/lib-dynload/_struct.so
SOAnswer_T 6828  jon  mem    REG   253,0    37180   91249 /usr/lib/python2.6/lib-dynload/arraymodule.so
SOAnswer_T 6828  jon  mem    REG   253,0    30496   16167 /usr/lib/python2.6/lib-dynload/operator.so
SOAnswer_T 6828  jon  mem    REG   253,0    10448   16137 /usr/lib/python2.6/lib-dynload/_randommodule.so
SOAnswer_T 6828  jon  mem    REG   253,0    13552   16157 /usr/lib/python2.6/lib-dynload/fcntlmodule.so
SOAnswer_T 6828  jon  mem    REG   253,0    17152   91253 /usr/lib/python2.6/lib-dynload/cStringIO.so
SOAnswer_T 6828  jon  mem    REG   253,0    11648   12778 /lib/libcom_err.so.2.1
SOAnswer_T 6828  jon  mem    REG   253,0    19660   16148 /usr/lib/python2.6/lib-dynload/binascii.so
SOAnswer_T 6828  jon  mem    REG   253,0     8224   12704 /lib/libkeyutils-1.2.so
SOAnswer_T 6828  jon  mem    REG   253,0    28920   91246 /usr/lib/python2.6/lib-dynload/_ssl.so
SOAnswer_T 6828  jon  mem    REG   253,0    36580   15554 /lib/libkrb5support.so.0.1
SOAnswer_T 6828  jon  mem    REG   253,0    14640   20456 /lib/libutil-2.12.2.so
SOAnswer_T 6828  jon  mem    REG   253,0   141532    4868 /lib/ld-2.12.2.so
SOAnswer_T 6828  jon  mem    REG   253,0  1851728    4869 /lib/libc-2.12.2.so
SOAnswer_T 6828  jon  mem    REG   253,0   202044    5741 /lib/libm-2.12.2.so
SOAnswer_T 6828  jon  mem    REG   253,0    19788    4870 /lib/libdl-2.12.2.so
SOAnswer_T 6828  jon  mem    REG   253,0   133136    5431 /lib/libpthread-2.12.2.so
SOAnswer_T 6828  jon  mem    REG   253,0    76368    5748 /lib/libz.so.1.2.3
SOAnswer_T 6828  jon  mem    REG   253,0   122420    8431 /lib/libselinux.so.1
SOAnswer_T 6828  jon  mem    REG   253,0   101068    8430 /lib/libresolv-2.12.2.so
SOAnswer_T 6828  jon  mem    REG   253,0    25476   16120 /usr/lib/python2.6/lib-dynload/_collectionsmodule.so
SOAnswer_T 6828  jon  mem    REG   253,0    58404   16141 /usr/lib/python2.6/lib-dynload/_socketmodule.so
SOAnswer_T 6828  jon  mem    REG   253,0    11500   91240 /usr/lib/python2.6/lib-dynload/_hashlib.so
SOAnswer_T 6828  jon  mem    REG   253,0     6280   91263 /usr/lib/python2.6/lib-dynload/syslog.so
SOAnswer_T 6828  jon  mem    REG   253,0    22076   16164 /usr/lib/python2.6/lib-dynload/mathmodule.so
SOAnswer_T 6828  jon  mem    REG   253,0    16748   91265 /usr/lib/python2.6/lib-dynload/timemodule.so
SOAnswer_T 6828  jon  mem    REG   253,0     7616   16111 /usr/lib/python2.6/lib-dynload/_bisectmodule.so
SOAnswer_T 6828  jon  mem    REG   253,0    22560   16175 /usr/lib/python2.6/lib-dynload/stropmodule.so
SOAnswer_T 6828  jon  mem    REG   253,0  1603772   19175 /usr/lib/libpython2.6.so.1.0
SOAnswer_T 6828  jon  mem    REG   253,0   190528   63751 /lib/libgssapi_krb5.so.2.2
SOAnswer_T 6828  jon  mem    REG   253,0   758712   22619 /lib/libkrb5.so.3.3
SOAnswer_T 6828  jon  mem    REG   253,0   177868   20371 /lib/libk5crypto.so.3.1
SOAnswer_T 6828  jon  mem    REG   253,0  1596908   63969 /lib/libcrypto.so.1.0.0d
SOAnswer_T 6828  jon  mem    REG   253,0   358704   64033 /usr/lib/libssl.so.1.0.0d
SOAnswer_T 6828  jon  mem    REG   253,0 99158720   95278 /usr/lib/locale/locale-archive
SOAnswer_T 6828  jon    0u   CHR   136,2      0t0       5 /dev/pts/2
SOAnswer_T 6828  jon    1w  FIFO     0,8      0t0 2254540 pipe
SOAnswer_T 6828  jon    2u   CHR   136,2      0t0       5 /dev/pts/2
SOAnswer_T 6828  jon    3u  IPv4 2254907      0t0     TCP blah:36050->blah2.com.br:http (ESTABLISHED)

, -aU, :

[ 11:46 root@hozbox /proc/6828 ]# lsof -aU -p 1511
COMMAND  PID USER   FD   TYPE     DEVICE SIZE/OFF  NODE NAME
acpid   1511 root    4u  unix 0xd9063800      0t0 10860 /var/run/acpid.socket
acpid   1511 root    6u  unix 0xda79c200      0t0 10876 socket

/proc/PID/fd fd .

man lsof

: . , ?

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Source: https://habr.com/ru/post/1720971/

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