fix(inputs.netflow): Decode flags in TCP and IP headers correctly

[joseluisgonzalezca]

Summary

This problem is present during IPv4 header decoding and TCP header decoding. Both issues have been fixed in this PR.
Golang switch block does not do automatic fallthrough so it must be explicitly added to handle multiple cases

Checklist

• No AI generated code was used in this PR

Related issues

resolves issue #16247

[telegraf-tiger]

Download PR build artifacts for linux_amd64.tar.gz, darwin_arm64.tar.gz, and windows_amd64.zip.
Downloads for additional architectures and packages are available below.

👍 This pull request doesn't change the Telegraf binary size

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Artifact URLs

DEB	RPM	TAR GZ	ZIP
amd64.deb	aarch64.rpm	darwin_amd64.tar.gz	windows_amd64.zip
arm64.deb	armel.rpm	darwin_arm64.tar.gz	windows_arm64.zip
armel.deb	armv6hl.rpm	freebsd_amd64.tar.gz	windows_i386.zip
armhf.deb	i386.rpm	freebsd_armv7.tar.gz
i386.deb	ppc64le.rpm	freebsd_i386.tar.gz
mips.deb	riscv64.rpm	linux_amd64.tar.gz
mipsel.deb	s390x.rpm	linux_arm64.tar.gz
ppc64el.deb	x86_64.rpm	linux_armel.tar.gz
riscv64.deb		linux_armhf.tar.gz
s390x.deb		linux_i386.tar.gz
		linux_mips.tar.gz
		linux_mipsel.tar.gz
		linux_ppc64le.tar.gz
		linux_riscv64.tar.gz
		linux_s390x.tar.gz

[joseluisgonzalezca]

I have tested the PR build artefact in a real environment and it's working as expected. All flags are decoded and included into the metrics:

[srebhan]

Thanks a lot for spotting this @joseluisgonzalezca! The contribution is much appreciated!

Could you please also check the other decoders!?!

[joseluisgonzalezca]

Thanks a lot for spotting this @joseluisgonzalezca! The contribution is much appreciated!

Could you please also check the other decoders!?!

Hi Sven,

I've reviewed the sFlow decoder source code and I haven't detected any additional issues. Nevertheless, we are actively using the plugin and checking received metrics. As soon as I found any anomaly, I will report it and try to solve it.

Thanks!