From d3725224734e87dcd57998f5efef0f0f58d20c1e Mon Sep 17 00:00:00 2001
From: Luca Boccassi <luca.boccassi@gmail.com>
Date: Tue, 11 Nov 2025 00:34:24 +0000
Subject: [PATCH] Install sysusers.d config for 'tcpdump' user/group

Ubuntu, Fedora and other distro create the tcpdump user/group
pair by default, to be used for unprivileged access to tcpdump:

https://git.launchpad.net/ubuntu/+source/tcpdump/tree/debian/tcpdump.postinst
https://src.fedoraproject.org/rpms/tcpdump/blob/rawhide/f/tcpdump-sysusers.conf

Add a sysusers.d config file and install it. This configuration
file will create the 'tcpdump' user/group pair on first boot/factory
reset/package installation, without requiring manual scripts or actions.
This is very important for image-based OSes, but it is useful in other
cases too, to allow using declarative configuration instead of scripts.

RPM now has built-in support for sysusers.d too.

https://www.freedesktop.org/software/systemd/man/latest/sysusers.d.html

This is just a one-line config file, so if a system doesn't support
sysusers.d, it is a harmless no-op (and can be deleted/not packaged
too).
---
 Makefile.in           | 5 +++++
 tcpdump-sysusers.conf | 1 +
 2 files changed, 6 insertions(+)
 create mode 100644 tcpdump-sysusers.conf

diff --git a/Makefile.in b/Makefile.in
index fc102099c..f9d8bbc7d 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -369,6 +369,7 @@ EXTRA_DIST = \
 	send-ack.awk \
 	smbutil.c \
 	stime.awk \
+	tcpdump-sysusers.conf \
 	tcpdump.1.in
 
 TEST_DIST= `git -C "$$DIR" ls-files tests`
@@ -405,11 +406,15 @@ install: all
 	[ -d $(DESTDIR)$(mandir)/man1 ] || \
 	    (mkdir -p $(DESTDIR)$(mandir)/man1; chmod 755 $(DESTDIR)$(mandir)/man1)
 	$(INSTALL_DATA) $(PROG).1 $(DESTDIR)$(mandir)/man1/$(PROG).1
+	[ -d $(DESTDIR)$(prefix)/lib/sysusers.d ] || \
+	    (mkdir -p $(DESTDIR)$(prefix)/lib/sysusers.d; chmod 755 $(DESTDIR)$(prefix)/lib/sysusers.d)
+	$(INSTALL_DATA) tcpdump-sysusers.conf $(DESTDIR)$(prefix)/lib/sysusers.d/tcpdump.conf
 
 uninstall:
 	rm -f $(DESTDIR)$(bindir)/$(PROG)
 	rm -f $(DESTDIR)$(bindir)/$(PROG).`cat ${srcdir}/VERSION`
 	rm -f $(DESTDIR)$(mandir)/man1/$(PROG).1
+	rm -f $(DESTDIR)$(prefix)/lib/sysusers.d/tcpdump.conf
 
 lint:
 	lint -hbxn $(SRC) $(LIBNETDISSECT_SRC) | \
diff --git a/tcpdump-sysusers.conf b/tcpdump-sysusers.conf
new file mode 100644
index 000000000..c85914c2f
--- /dev/null
+++ b/tcpdump-sysusers.conf
@@ -0,0 +1 @@
+u! tcpdump - "tcpdump" /nonexistent