Decrease optmem_max preset to 40960

Let the build fail, if the minimum kernel version cannot be met
Conditionalize the sysctl.d tweak on version of the kernel
Conditionalize the name of README.distro on the distro

libkcapi.spec

@@ -6,11 +6,28 @@
 # Do we build the replacements package?
 %bcond_with replacements
 
+# This package needs at least Linux Kernel v4.10.0.
+%global min_kernel_ver    4.10.0
+
+# Do we need to tweak sysctl.d? In newer versions of the Linux
+# Kernel the default ancillary buffer size is set high enough.
+# TODO: Adapt this when the patch for net/core/sock.c is merged.
+%if %{lua:print(rpm.vercmp('99.0.0', posix.uname('%r')));} >= 0
+%global with_sysctl_tweak 1
+%else
+%global with_sysctl_tweak 0
+%endif
+
+%if %{with_sysctl_tweak}
 # Priority for the sysctl.d preset.
 %global sysctl_prio       50
 
 # Value used for the sysctl.d preset.
-%global sysctl_optmem_max 81920
+%global sysctl_optmem_max 40960
+
+# Extension for the README.distro file.
+%global distroname_ext    %{?fedora:fedora}%{?rhel:redhat}
+%endif
 
 # Lowest limit to run the testsuite.  If we cannot obtain this
 # value, we asume the testsuite cannot be run.
@@ -63,7 +80,7 @@
 
 Name:           libkcapi
 Version:        %{vmajor}.%{vminor}.%{vpatch}
-Release:        1%{?dist}
+Release:        2%{?dist}
 Summary:        User space interface to the Linux Kernel Crypto API
 
 License:        BSD or GPLv2
@@ -91,6 +108,12 @@ BuildRequires:  openssl
 BuildRequires:  systemd
 BuildRequires:  xmlto
 
+# To make sure this is not buildable nor installable if the
+# available Linux Kernel does not support the Linux Kernel
+# Crypto API User Space Interface.
+BuildRequires:  kernel-headers >= %{min_kernel_ver}
+Requires:       kernel         >= %{min_kernel_ver}
+
 # For ownership of %%{_sysctldir}.
 Requires:       systemd
 
@@ -191,7 +214,8 @@ generators implemented in the Linux kernel from command line.
 %prep
 %autosetup -p 1
 
-%{__cat} << EOF > README.fedora
+%if %{with_sysctl_tweak}
+%{__cat} << EOF > README.%{distroname_ext}
 This package increases the default limit of the ancillary buffer size
 per kernel socket defined in \`net.core.optmem_max\` to %{sysctl_optmem_max} bytes.
 
@@ -213,7 +237,7 @@ if you need or want to override the preset made by this package.
 EOF
 
 %{__cat} << EOF > %{sysctl_prio}-%{name}-optmem_max.conf
-# See the 'README.fedora' file shipped in %%doc
+# See the 'README.%{distroname_ext}' file shipped in %%doc
 # with the %{name} package.
 #
 # See '%{_sysctldir}/50-default.conf',
@@ -222,6 +246,7 @@ EOF
 # Increase the ancillary buffer size per socket.
 net.core.optmem_max = %{sysctl_optmem_max}
 EOF
+%endif
 
 %{_bindir}/autoreconf -fiv
 
@@ -246,13 +271,17 @@ EOF
 %make_install
 
 # Install sysctl.d preset.
+%{__mkdir_p} %{buildroot}%{_sysctldir}
 %{__install} -Dpm 0644 -t %{buildroot}%{_sysctldir} \
   %{sysctl_prio}-%{name}-optmem_max.conf
 
 # Install into proper location for inclusion by %%doc.
+%{__mkdir_p} %{buildroot}%{_pkgdocdir}
 %{__install} -Dpm 0644 -t %{buildroot}%{_pkgdocdir} \
-  README.fedora README.md CHANGES TODO              \
-  doc/%{name}.p{df,s}
+%if %{with_sysctl_tweak}
+  README.%{distroname_ext}                          \
+%endif
+  README.md CHANGES TODO doc/%{name}.p{df,s}
 %{__cp} -pr lib/doc/html %{buildroot}%{_pkgdocdir}
 
 %if !%{with replacements}
@@ -312,14 +341,16 @@ popd
 
 %files
 %doc %dir %{_pkgdocdir}
-%doc %{_pkgdocdir}/README.fedora
 %doc %{_pkgdocdir}/README.md
 %license COPYING*
 /%{_lib}/%{name}.so.%{vmajor}
 /%{_lib}/%{name}.so.%{version}
 /%{_lib}/.%{name}.so.%{vmajor}.hmac
 /%{_lib}/.%{name}.so.%{version}.hmac
+%if %{with_sysctl_tweak}
+%doc %{_pkgdocdir}/README.%{distroname_ext}
 %{_sysctldir}/%{sysctl_prio}-%{name}-optmem_max.conf
+%endif
 
 
 %files          devel
@@ -383,6 +414,12 @@ popd
 
 
 %changelog
+* Wed Jan 17 2018 Björn Esser <besser82@fedoraproject.org> - 1.0.3-2
+- Decrease optmem_max preset to 40960
+- Let the build fail, if the minimum kernel version cannot be met
+- Conditionalize the sysctl.d tweak on version of the kernel
+- Conditionalize the name of README.distro on the distro
+
 * Tue Jan 16 2018 Björn Esser <besser82@fedoraproject.org> - 1.0.3-1
 - Initial import (rhbz#1533929)