Engineer from Télécom Paris
Ph.D Thesis from UPMC

Network & Security IT - Le RSI
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ISPEED/OSPEED PATCH FOR SOCAT

Patch for SOCAT correcting a bug when changing default speed of a serial asynchronous line, that occurs on some systems like FreeBSD.


SYNOPSYS

With SOCAT (at least up to version 1.7.3.1) on systems where b0 to b4000000 options are not available, like FreeBSD, setting the speed of a TERMIOS terminal is done using the ispeed and ospeed options.

But when using simultaneously ispeed and ospeed parameters with SOCAT, the speed values are set within two distinct ioctl requests, so changing the speed of terminals or devices that need matching input and output returns an Invalid argument error (the TIOCSETA/TIOCSETAW/TIOCSETAF ioctl returns -1 and sets errno to EINVAL).

This is especially the case On FreeBSD, where many tty device drivers need matching input and output speeds:
  • - those that depend on ucom(4): uark(4), ubsa(4), ubser(4), uftdi(4), umcs(4), uplcom(4), uslcom(4), uvscom(4)
  • - some others, even not depending on ucom(4): uart(4), sio(4), digi(4), rp(4)
But some don't: tty(4)

With those drivers, the input and output speeds must match and be set inside a single ioctl request (TIOCSETA, TIOCSETAW or TIOCSETAF). The only exception to this rule is when the input baud rate is zero because, according to POSIX, in that case, the input baud rate is set equal to the output baud rate.

For instance, this call to SOCAT on FreeBSD 10.1 terminates immediately with an EINVAL error:
# socat -d /dev/cuaU2,ispeed=57600,ospeed=57600,echo=0,raw TCP-LISTEN:9000,reuseaddr
2015/03/09 00:43:33 socat[20723] E tcsetattr(3, TCSADRAIN, 0x7fffffffe148): Invalid argument

The status of the bug report on FreeBSD: Bug 198441


INSTALLING ON FreeBSD FROM THE PORTS TREE

- change directory to the SOCAT port directory:
# cd /usr/ports/net/socat
- download the patch: patch.diff
# fetch http://fenyo.net/newweb/socat/patch/patch.diff
- add the patch file to the port:
# mv patch.diff files/patch-xioopts.c
- compile and install the port:
# make
# make install

INSTALLING ON FreeBSD FROM THE PATCHED PORT

- download the SOCAT patched port: socat-port-patched.tar.gz
# fetch http://fenyo.net/newweb/socat/socat-port-patched.tar.gz
- compile and install the port:
# tar zxf socat-port-patched.tar.gz
# cd socat
# make
# make install

Note: you can also download the compiled patched port (compiled for amd64 on 10.1-RELEASE).

INSTALLING ON FreeBSD FROM THE PATCHED PACKAGE

- download the SOCAT patched package: socat-1.7.3.0_1-patched.txz
# fetch http://fenyo.net/newweb/socat/socat-port-patched.tar.gz
- install the package:
# pkg install socat-1.7.3.0_1-patched.txz

INSTALLING FROM THE SOURCES

- download the sources: socat-1.7.3.0.tar.gz
# fetch http://fenyo.net/newweb/socat/socat-1.7.3.0.tar.gz
# tar zxf socat-1.7.3.0.tar.gz

- download the patch: patch.diff
# fetch http://fenyo.net/newweb/socat/patch/patch.diff
- patch the sources:
# cd socat-1.7.3.0
# patch < ../patch.diff
- compile and install SOCAT:
# autoconf
# ./configure
# make
# make install

INSTALLING FROM THE PATCHED SOURCE TREE

- download the patched source tree: socat-1.7.3.0-patched.tar.gz
# fetch http://fenyo.net/newweb/socat/socat-1.7.3.0-patched.tar.gz
# tar zxf socat-1.7.3.0-patched.tar.gz
- compile and install SOCAT:
# cd socat-1.7.3.0-patched
# autoconf
# ./configure
# make
# make install

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