Enhancement #416 non blocking stdin #448
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While on BSD systems, tcprewrite likely sets `O_NDELAY` which is proper for most posix systems as this is the newer flag and they likely treat both similarly. However BSD and unix derivatives should likely utilize `FIONBIO` due to known issues with reading from tty with a 0 byte read returning -1 opposed to 0. Reference comment 1: https://stackoverflow.com/questions/1150635/unix-nonblocking-i-o-o-nonblock-vs-fionbio on behalf of Cisco Talos
Avoid non-blocking behaviour when using STDIN
src/tcprewrite.c
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| @@ -149,6 +152,10 @@ main(int argc, char *argv[]) | |||
| #ifdef ENABLE_DMALLOC | |||
| dmalloc_shutdown(); | |||
| #endif | |||
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| /* avoid making STDIN non-blocking */ | |||
| ioctl(0, FIONBIO, &nb); | |||
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@dlangille some questions/comments
- PR Avoid non-blocking behaviour when using STDIN #416 has a compile issue fixed int this PR
- I don't understand why this is implemented just before the exiting the program.
- Is this fixing any particular issue?
- If so, should it not be applied to other
main()procedures (e.g.tcpreplay)?
I am pulling this PR out of 4.3 project until I receive clarification.
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I am relaying for the dev who found the issue.
tcprewrite (and likely tcpreplay see: https://stackoverflow.com/questions/16402363/read-fails-after-tcpreplay-with-error-0-resource-temporarily-unavailabl) sets STDIN as non-blocking and then doesn't set it back to blocking on exit, which causes reads to fail after exit. Example:
$ tcprewrite -C -i in.pcap -o out.pcap
$ cat > foo
cat: -: Resource temporarily unavailable
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I applied your change to all executables. Thanks for the contribution.
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Much appreciated. Thanks for finding that other stuff.
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