libs: make privilege elevation thread-safe

[mjstapp]

Privs escalation is process-wide, and a multi-threaded process can deadlock. This adds a mutex and a counter to the privs object, preventing multiple threads from racing for the privs escalation system call.

Related Issue

#3910

Components

libs

[LabN-CI]

💚 Basic BGPD CI results: SUCCESS, 0 tests failed

Results table

_	_
Result	SUCCESS git merge/3911 db120f2
Date	03/05/2019
Start	15:55:16
Finish	16:19:20
Run-Time	24:04
Total	1813
Pass	1813
Fail	0
Valgrind-Errors	0
Valgrind-Loss	0
Details	vncregress-2019-03-05-15:55:16.txt
Log	autoscript-2019-03-05-15:55:57.log.bz2
Memory	496 499 429

For details, please contact louberger

[LabN-CI]

💚 Basic BGPD CI results: SUCCESS, 0 tests failed

Results table

_	_
Result	SUCCESS git merge/3911 c5c44d4
Date	03/05/2019
Start	16:20:30
Finish	16:44:25
Run-Time	23:55
Total	1813
Pass	1813
Fail	0
Valgrind-Errors	0
Valgrind-Loss	0
Details	vncregress-2019-03-05-16:20:30.txt
Log	autoscript-2019-03-05-16:21:23.log.bz2
Memory	502 505 429

For details, please contact louberger

[NetDEF-CI]

Continuous Integration Result: SUCCESSFUL

Congratulations, this patch passed basic tests

Tested-by: NetDEF / OpenSourceRouting.org CI System

CI System Testrun URL: https://ci1.netdef.org/browse/FRR-FRRPULLREQ-6899/

This is a comment from an automated CI system.
For questions and feedback in regards to this CI system, please feel free to email
Martin Winter - mwinter (at) opensourcerouting.org.

Warnings Generated during build:

Ubuntu 16.04 i386 build: Successful with additional warnings

Debian Package lintian failed for Ubuntu 16.04 i386 build:
(see full package build log at https://ci1.netdef.org/browse/FRR-FRRPULLREQ-6899/artifact/U1604I386/ErrorLog/log_lintian.txt)

W: frr-rpki-rtrlib: package-has-long-file-name 71 (81) > 80

Ubuntu 18.04 amd64 build: Successful with additional warnings

Debian Package lintian failed for Ubuntu 18.04 amd64 build:
(see full package build log at https://ci1.netdef.org/browse/FRR-FRRPULLREQ-6899/artifact/U1804AMD64/ErrorLog/log_lintian.txt)

W: frr-rpki-rtrlib: package-has-long-file-name 72 (81) > 80

Ubuntu 14.04 amd64 build: Successful with additional warnings

Debian Package lintian failed for Ubuntu 14.04 amd64 build:
(see full package build log at https://ci1.netdef.org/browse/FRR-FRRPULLREQ-6899/artifact/CI001BUILD/ErrorLog/log_lintian.txt)

W: frr-rpki-rtrlib: package-has-long-file-name 72 (81) > 80

Debian 9 amd64 build: Successful with additional warnings

Debian Package lintian failed for Debian 9 amd64 build:
(see full package build log at https://ci1.netdef.org/browse/FRR-FRRPULLREQ-6899/artifact/CI021BUILD/ErrorLog/log_lintian.txt)

W: frr-rpki-rtrlib-dbgsym: package-has-long-file-name 72 (81) > 80

Ubuntu 16.04 amd64 build: Successful with additional warnings

Debian Package lintian failed for Ubuntu 16.04 amd64 build:
(see full package build log at https://ci1.netdef.org/browse/FRR-FRRPULLREQ-6899/artifact/CI014BUILD/ErrorLog/log_lintian.txt)

W: frr-rpki-rtrlib: package-has-long-file-name 72 (81) > 80

---

CLANG Static Analyzer Summary

• Github Pull Request 3911, comparing to Git base SHA b19abe1
• Base image data for Git b19abe1 does not exist - compare skipped

3 Static Analyzer issues remaining.

See details at
https://ci1.netdef.org/browse/FRR-FRRPULLREQ-6899/artifact/shared/static_analysis/index.html