Public bug reported:
The options "fdin=x,fdout=y" are used to create file descriptors in order to
have scripts that are executed via EXEC communicate with the socket.
After heaps of debugging, I noticed that the output file descriptor is never
actually opened by socat (although it says otherwise).
Please see the output of socat and the corresponding script, which executes
"filan" to display currently open FDs.
You can see that FD3 is open and input is processed. However, when
writing to FD4, the error message "Bad file descriptor" appears (not
shown in log). FD4 is clearly never opened (what would have been
expected behaviour)
# socat -d -d -u TCP4-LISTEN:80,reuseaddr,fork,su=nobody
EXEC:./script.sh,fdout=4,fdin=3 | tee connlog.log
2014/08/19 15:26:15 socat[26813] N listening on AF=2 0.0.0.0:80
2014/08/19 15:26:19 socat[26813] N accepting connection from AF=2 1.2.3.4:49874
on AF=2 4.5.6.7:80
2014/08/19 15:26:19 socat[26813] N forked off child process 26815
2014/08/19 15:26:19 socat[26813] N listening on AF=2 0.0.0.0:80
2014/08/19 15:26:19 socat[26815] N forking off child, using socket for writing
2014/08/19 15:26:19 socat[26815] N forked off child process 26816
2014/08/19 15:26:19 socat[26815] N forked off child process 26816
2014/08/19 15:26:19 socat[26815] N starting data transfer loop with FDs [4,4]
and [3,3]
2014/08/19 15:26:19 socat[26816] N execvp'ing "./script.sh"
[SCRIPT] Received http request.
FD type device inode mode links uid gid rdev size
blksize blocks atime mtime
ctime cloexec flags sigown sigio
0: chrdev 0,12 5 020620 1 0 5 136,2 0
1024 0 Tue Aug 19 15:26:08 2014 Tue Aug 19 15:26:16 2014
Thu Jul 17 21:36:34 2014 0 x008002 0 0
(no STREAMS modules) /dev/pts/2 IFLAGS=00000500 OFLAGS=00000005
CFLAGS=000000bf LFLAGS=00008a3b cc[0]=^C cc[1]=^\ cc[2]=x7F cc[3]=^U cc[4]=^D
cc[5]=^@ cc[6]=^A cc[7]=^@ cc[8]=^Q cc[9]=^S cc[10]=^Z cc[11]=^@ cc[12]=^R
cc[13]=^O cc[14]=^W cc[15]=^V cc[16]=^@ cc[17]=^@ cc[18]=^@ cc[19]=^@ cc[20]=^@
cc[21]=^@ cc[22]=^@ cc[23]=^@ cc[24]=^@ cc[25]=^@ cc[26]=^@ cc[27]=^@ cc[28]=^@
cc[29]=^@ cc[30]=^@ cc[31]=^@poll: OUT,
1: pipe 0,8 17895603 010600 1 0 0 0,0
0 4096 0 Tue Aug 19 15:26:19 2014 Tue Aug 19 15:26:19
2014 Tue Aug 19 15:26:19 2014 0 x000001 0 0
(no STREAMS modules)poll: OUT,
2: chrdev 0,12 5 020620 1 0 5 136,2 0
1024 0 Tue Aug 19 15:26:08 2014 Tue Aug 19 15:26:16 2014
Thu Jul 17 21:36:34 2014 0 x008002 0 0
(no STREAMS modules) /dev/pts/2 IFLAGS=00000500 OFLAGS=00000005
CFLAGS=000000bf LFLAGS=00008a3b cc[0]=^C cc[1]=^\ cc[2]=x7F cc[3]=^U cc[4]=^D
cc[5]=^@ cc[6]=^A cc[7]=^@ cc[8]=^Q cc[9]=^S cc[10]=^Z cc[11]=^@ cc[12]=^R
cc[13]=^O cc[14]=^W cc[15]=^V cc[16]=^@ cc[17]=^@ cc[18]=^@ cc[19]=^@ cc[20]=^@
cc[21]=^@ cc[22]=^@ cc[23]=^@ cc[24]=^@ cc[25]=^@ cc[26]=^@ cc[27]=^@ cc[28]=^@
cc[29]=^@ cc[30]=^@ cc[31]=^@poll: OUT,
3: socket 0,7 17891857 0140777 1 65534 65534 0,0
0 4096 0 Thu Jan 1 01:00:00 1970 Thu Jan 1 01:00:00
1970 Thu Jan 1 01:00:00 1970 0 x000002 0 0
(no STREAMS modules)DEBUG=0 REUSEADDR=0 TYPE=1 ERROR=0 DONTROUTE=0
BROADCAST=0 SNDBUF=212992 RCVBUF=212992 KEEPALIVE=0 OOBINLINE=0
NO_CHECK=0 PRIORITY=0 LINGER={0,0} BSDCOMPAT=0 REUSEPORT=0
PASSCRED=0 PEERCRED={26815,65534} RCVLOWAT=1 SNDLOWAT=1
RCVTIMEO={0,0} SNDTIMEO={0,0} BINDTODEVICE={0,0}
ATTACH_FILTER={0,0} AF=1 "<anon>" <-> AF=1 "<anon>" poll:
IN,OUT,; FIONREAD=353; recvmsg=1,
releases
# lsb_release -rd
Description: Ubuntu 14.04 LTS
Release: 14.04
# apt-cache policy socat
socat:
Installed: 1.7.2.3-1
Candidate: 1.7.2.3-1
3) and 4) -> see above.
Thanks a lot for processing this bug.
** Affects: socat (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1358748
Title:
socat fdout option will not open output file descriptor
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