[RFC PATCH for-7.1] Remove the slirp submodule (and only compile with an external libslirp)

[Thomas Huth]

QEMU 7.1 won't support Ubuntu 18.04 anymore, so the last big important
distro that did not have a pre-packaged libslirp has been dismissed.
All other major distros seem to have a libslirp package in their
distribution already - according to repology.org:

          Fedora 34: 4.4.0
  CentOS 8 (RHEL-8): 4.4.0
      Debian Buster: 4.3.1 (in buster-backports)
 OpenSUSE Leap 15.3: 4.3.1
   Ubuntu LTS 20.04: 4.1.0
      FreeBSD Ports: 4.6.1
      NetBSD pkgsrc: 4.3.1
           Homebrew: 4.6.1
        MSYS2 mingw: 4.6.1

The only one that still seems to be missing a libslirp package is
OpenBSD - but I assume that they can add it to their ports system
quickly if required.

So there is no real urgent need for keeping the slirp submodule in
the QEMU tree anymore. Thus let's drop the slirp submodule now and
rely on the libslirp packages from the distributions instead.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 configure                     |  22 +------
 meson.build                   | 112 +++++-----------------------------
 .gitlab-ci.d/buildtest.yml    |  19 +++---
 .gitmodules                   |   3 -
 MAINTAINERS                   |   1 -
 meson_options.txt             |   5 +-
 scripts/archive-source.sh     |   2 +-
 scripts/meson-buildoptions.sh |   4 +-
 slirp                         |   1 -
 9 files changed, 29 insertions(+), 140 deletions(-)
 delete mode 160000 slirp

diff --git a/configure b/configure
index 7c08c18358..3aedff78a9 100755
--- a/configure
+++ b/configure
@@ -339,10 +339,8 @@ skip_meson=no
 # 1. Track which submodules are needed
 if test "$default_feature" = no ; then
   capstone="disabled"
-  slirp="disabled"
 else
   capstone="auto"
-  slirp="auto"
 fi
 fdt="auto"
 
@@ -874,14 +872,6 @@ for opt do
   ;;
   --disable-tsan) tsan="no"
   ;;
-  --disable-slirp) slirp="disabled"
-  ;;
-  --enable-slirp) slirp="enabled"
-  ;;
-  --enable-slirp=git) slirp="internal"
-  ;;
-  --enable-slirp=*) slirp="$optarg"
-  ;;
   --disable-xen) xen="disabled"
   ;;
   --enable-xen) xen="enabled"
@@ -2576,16 +2566,6 @@ EOF
   fi
 fi
 
-##########################################
-# check for slirp
-
-case "$slirp" in
-  auto | enabled | internal)
-    # Simpler to always update submodule, even if not needed.
-    git_submodules="${git_submodules} slirp"
-    ;;
-esac
-
 ##########################################
 # check for usable __NR_keyctl syscall
 
@@ -3169,7 +3149,7 @@ if test "$skip_meson" = no; then
         -Db_pie=$(if test "$pie" = yes; then echo true; else echo false; fi) \
         -Db_coverage=$(if test "$gcov" = yes; then echo true; else echo false; 
fi) \
         -Db_lto=$lto -Dcfi=$cfi -Dtcg=$tcg -Dxen=$xen \
-        -Dcapstone=$capstone -Dfdt=$fdt -Dslirp=$slirp \
+        -Dcapstone=$capstone -Dfdt=$fdt \
         $(test -n "${LIB_FUZZING_ENGINE+xxx}" && echo 
"-Dfuzzing_engine=$LIB_FUZZING_ENGINE") \
         $(if test "$default_feature" = no; then echo 
"-Dauto_features=disabled"; fi) \
         "$@" $cross_arg "$PWD" "$source_path"
diff --git a/meson.build b/meson.build
index 861de93c4f..5d93030da5 100644
--- a/meson.build
+++ b/meson.build
@@ -560,6 +560,20 @@ else
                          method: 'pkg-config', kwargs: static_kwargs)
 endif
 
+slirp = not_found
+if not get_option('slirp').auto() or have_system
+  slirp = dependency('slirp', required: get_option('slirp'),
+                     method: 'pkg-config', kwargs: static_kwargs)
+  # We cannot compile QEMU with CFI and libslirp enabled at the same time.
+  # This is because we register slirp functions as callbacks for QEMU Timers.
+  # When using a system-wide shared libslirp, the type information for the
+  # callback is missing and the timer call produces a false positive with CFI.
+  if get_option('cfi')
+    error('Control-Flow Integrity is not compatible with libslirp.' \
+           + ' Please configure with --disable-slirp')
+  endif
+endif
+
 vde = not_found
 if not get_option('vde').auto() or have_system or have_tools
   vde = cc.find_library('vdeplug', has_headers: ['libvdeplug.h'],
@@ -2406,100 +2420,6 @@ if capstone_opt == 'internal'
                                 include_directories: 
'capstone/include/capstone')
 endif
 
-slirp = not_found
-slirp_opt = 'disabled'
-if have_system
-  slirp_opt = get_option('slirp')
-  if slirp_opt in ['enabled', 'auto', 'system']
-    have_internal = fs.exists(meson.current_source_dir() / 'slirp/meson.build')
-    slirp = dependency('slirp', kwargs: static_kwargs,
-                       method: 'pkg-config',
-                       required: slirp_opt == 'system' or
-                                 slirp_opt == 'enabled' and not have_internal)
-    if slirp.found()
-      slirp_opt = 'system'
-    elif have_internal
-      slirp_opt = 'internal'
-    else
-      slirp_opt = 'disabled'
-    endif
-  endif
-  if slirp_opt == 'internal'
-    slirp_deps = []
-    if targetos == 'windows'
-      slirp_deps = cc.find_library('iphlpapi')
-    elif targetos == 'darwin'
-      slirp_deps = cc.find_library('resolv')
-    endif
-    slirp_conf = configuration_data()
-    slirp_conf.set('SLIRP_MAJOR_VERSION', 
meson.project_version().split('.')[0])
-    slirp_conf.set('SLIRP_MINOR_VERSION', 
meson.project_version().split('.')[1])
-    slirp_conf.set('SLIRP_MICRO_VERSION', 
meson.project_version().split('.')[2])
-    slirp_conf.set_quoted('SLIRP_VERSION_STRING', meson.project_version())
-    slirp_cargs = ['-DG_LOG_DOMAIN="Slirp"']
-    slirp_files = [
-      'slirp/src/arp_table.c',
-      'slirp/src/bootp.c',
-      'slirp/src/cksum.c',
-      'slirp/src/dhcpv6.c',
-      'slirp/src/dnssearch.c',
-      'slirp/src/if.c',
-      'slirp/src/ip6_icmp.c',
-      'slirp/src/ip6_input.c',
-      'slirp/src/ip6_output.c',
-      'slirp/src/ip_icmp.c',
-      'slirp/src/ip_input.c',
-      'slirp/src/ip_output.c',
-      'slirp/src/mbuf.c',
-      'slirp/src/misc.c',
-      'slirp/src/ncsi.c',
-      'slirp/src/ndp_table.c',
-      'slirp/src/sbuf.c',
-      'slirp/src/slirp.c',
-      'slirp/src/socket.c',
-      'slirp/src/state.c',
-      'slirp/src/stream.c',
-      'slirp/src/tcp_input.c',
-      'slirp/src/tcp_output.c',
-      'slirp/src/tcp_subr.c',
-      'slirp/src/tcp_timer.c',
-      'slirp/src/tftp.c',
-      'slirp/src/udp.c',
-      'slirp/src/udp6.c',
-      'slirp/src/util.c',
-      'slirp/src/version.c',
-      'slirp/src/vmstate.c',
-    ]
-
-    configure_file(
-      input : 'slirp/src/libslirp-version.h.in',
-      output : 'libslirp-version.h',
-      configuration: slirp_conf)
-
-    slirp_inc = include_directories('slirp', 'slirp/src')
-    libslirp = static_library('slirp',
-                              build_by_default: false,
-                              sources: slirp_files,
-                              c_args: slirp_cargs,
-                              include_directories: slirp_inc)
-    slirp = declare_dependency(link_with: libslirp,
-                               dependencies: slirp_deps,
-                               include_directories: slirp_inc)
-  endif
-endif
-
-# For CFI, we need to compile slirp as a static library together with qemu.
-# This is because we register slirp functions as callbacks for QEMU Timers.
-# When using a system-wide shared libslirp, the type information for the
-# callback is missing and the timer call produces a false positive with CFI.
-#
-# Now that slirp_opt has been defined, check if the selected slirp is 
compatible
-# with control-flow integrity.
-if get_option('cfi') and slirp_opt == 'system'
-  error('Control-Flow Integrity is not compatible with system-wide slirp.' \
-         + ' Please configure with --enable-slirp=git')
-endif
-
 fdt = not_found
 if have_system
   fdt_opt = get_option('fdt')
@@ -3471,7 +3391,7 @@ summary_info += {'genisoimage':       
config_host['GENISOIMAGE']}
 if targetos == 'windows' and have_ga
   summary_info += {'wixl':            wixl}
 endif
-if slirp_opt != 'disabled' and have_system
+if slirp.found() and have_system
   summary_info += {'smbd':            have_slirp_smbd ? smbd_path : false}
 endif
 summary(summary_info, bool_yn: true, section: 'Host binaries')
@@ -3666,7 +3586,7 @@ summary_info += {'SDL image support': sdl_image}
 summary_info += {'GTK support':       gtk}
 summary_info += {'pixman':            pixman}
 summary_info += {'VTE support':       vte}
-summary_info += {'slirp support':     slirp_opt == 'internal' ? slirp_opt : 
slirp}
+summary_info += {'slirp support':     slirp}
 summary_info += {'libtasn1':          tasn1}
 summary_info += {'PAM':               pam}
 summary_info += {'iconv support':     iconv}
diff --git a/.gitlab-ci.d/buildtest.yml b/.gitlab-ci.d/buildtest.yml
index 0aea7ab84c..19dc9f4590 100644
--- a/.gitlab-ci.d/buildtest.yml
+++ b/.gitlab-ci.d/buildtest.yml
@@ -41,7 +41,7 @@ build-system-ubuntu:
     job: amd64-ubuntu2004-container
   variables:
     IMAGE: ubuntu2004
-    CONFIGURE_ARGS: --enable-docs --enable-fdt=system --enable-slirp=system
+    CONFIGURE_ARGS: --enable-docs --enable-fdt=system
     TARGETS: aarch64-softmmu alpha-softmmu cris-softmmu hppa-softmmu
       microblazeel-softmmu mips64el-softmmu
     MAKE_CHECK_ARGS: check-build
@@ -118,7 +118,7 @@ build-system-fedora:
   variables:
     IMAGE: fedora
     CONFIGURE_ARGS: --disable-gcrypt --enable-nettle --enable-docs
-             --enable-fdt=system --enable-slirp=system --enable-capstone=system
+             --enable-fdt=system --enable-capstone=system
     TARGETS: tricore-softmmu microblaze-softmmu mips-softmmu
       xtensa-softmmu m68k-softmmu riscv32-softmmu ppc-softmmu sparc64-softmmu
     MAKE_CHECK_ARGS: check-build
@@ -335,10 +335,8 @@ clang-user:
 # On gitlab runners, default value sometimes end up calling 2 lds concurrently 
and
 # triggers an Out-Of-Memory error
 #
-# Since slirp callbacks are used in QEMU Timers, slirp needs to be compiled 
together
-# with QEMU and linked as a static library to avoid false positives in CFI 
checks.
-# This can be accomplished by using -enable-slirp=git, which avoids the use of
-# a system-wide version of the library
+# Since slirp callbacks are used in QEMU Timers, we cannot use libslirp with
+# CFI builds, and thus have to disable it here.
 #
 # Split in three sets of build/check/avocado to limit the execution time of 
each
 # job
@@ -351,7 +349,7 @@ build-cfi-aarch64:
     AR: llvm-ar
     IMAGE: fedora
     CONFIGURE_ARGS: --cc=clang --cxx=clang++ --enable-cfi --enable-cfi-debug
-      --enable-safe-stack --enable-slirp=git
+      --enable-safe-stack --disable-slirp
     TARGETS: aarch64-softmmu
     MAKE_CHECK_ARGS: check-build
   timeout: 70m
@@ -393,7 +391,7 @@ build-cfi-ppc64-s390x:
     AR: llvm-ar
     IMAGE: fedora
     CONFIGURE_ARGS: --cc=clang --cxx=clang++ --enable-cfi --enable-cfi-debug
-      --enable-safe-stack --enable-slirp=git
+      --enable-safe-stack --disable-slirp
     TARGETS: ppc64-softmmu s390x-softmmu
     MAKE_CHECK_ARGS: check-build
   timeout: 70m
@@ -435,7 +433,7 @@ build-cfi-x86_64:
     AR: llvm-ar
     IMAGE: fedora
     CONFIGURE_ARGS: --cc=clang --cxx=clang++ --enable-cfi --enable-cfi-debug
-      --enable-safe-stack --enable-slirp=git
+      --enable-safe-stack --disable-slirp
     TARGETS: x86_64-softmmu
     MAKE_CHECK_ARGS: check-build
   timeout: 70m
@@ -469,7 +467,7 @@ tsan-build:
   variables:
     IMAGE: ubuntu2004
     CONFIGURE_ARGS: --enable-tsan --cc=clang-10 --cxx=clang++-10
-          --enable-trace-backends=ust --enable-fdt=system --enable-slirp=system
+          --enable-trace-backends=ust --enable-fdt=system --disable-slirp
     TARGETS: x86_64-softmmu ppc64-softmmu riscv64-softmmu x86_64-linux-user
     MAKE_CHECK_ARGS: bench V=1
 
@@ -571,7 +569,6 @@ build-without-default-features:
       --disable-capstone
       --disable-pie
       --disable-qom-cast-debug
-      --disable-slirp
       --disable-strip
     TARGETS: avr-softmmu i386-softmmu mips64-softmmu s390x-softmmu sh4-softmmu
       sparc64-softmmu hexagon-linux-user i386-linux-user s390x-linux-user
diff --git a/.gitmodules b/.gitmodules
index f4b6a9b401..d55cdb5036 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -49,9 +49,6 @@
 [submodule "roms/edk2"]
        path = roms/edk2
        url = https://gitlab.com/qemu-project/edk2.git
-[submodule "slirp"]
-       path = slirp
-       url = https://gitlab.com/qemu-project/libslirp.git
 [submodule "roms/opensbi"]
        path = roms/opensbi
        url =   https://gitlab.com/qemu-project/opensbi.git
diff --git a/MAINTAINERS b/MAINTAINERS
index 4ad2451e03..9a4fa68cc0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2924,7 +2924,6 @@ F: include/hw/registerfields.h
 SLIRP
 M: Samuel Thibault <samuel.thibault@ens-lyon.org>
 S: Maintained
-F: slirp/
 F: net/slirp.c
 F: include/net/slirp.h
 T: git https://people.debian.org/~sthibault/qemu.git slirp
diff --git a/meson_options.txt b/meson_options.txt
index 52b11cead4..668c859d84 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -173,6 +173,8 @@ option('l2tpv3', type : 'feature', value : 'auto',
        description: 'l2tpv3 network backend support')
 option('netmap', type : 'feature', value : 'auto',
        description: 'netmap network backend support')
+option('slirp', type: 'feature', value: 'auto',
+       description: 'libslirp user mode network backend support')
 option('vde', type : 'feature', value : 'auto',
        description: 'vde network backend support')
 option('virglrenderer', type : 'feature', value : 'auto',
@@ -223,9 +225,6 @@ option('virtiofsd', type: 'feature', value: 'auto',
 option('capstone', type: 'combo', value: 'auto',
        choices: ['disabled', 'enabled', 'auto', 'system', 'internal'],
        description: 'Whether and how to find the capstone library')
-option('slirp', type: 'combo', value: 'auto',
-       choices: ['disabled', 'enabled', 'auto', 'system', 'internal'],
-       description: 'Whether and how to find the slirp library')
 option('fdt', type: 'combo', value: 'auto',
        choices: ['disabled', 'enabled', 'auto', 'system', 'internal'],
        description: 'Whether and how to find the libfdt library')
diff --git a/scripts/archive-source.sh b/scripts/archive-source.sh
index c6169db69f..23e042dacd 100755
--- a/scripts/archive-source.sh
+++ b/scripts/archive-source.sh
@@ -26,7 +26,7 @@ sub_file="${sub_tdir}/submodule.tar"
 # independent of what the developer currently has initialized
 # in their checkout, because the build environment is completely
 # different to the host OS.
-submodules="dtc slirp meson ui/keycodemapdb"
+submodules="dtc meson ui/keycodemapdb"
 submodules="$submodules tests/fp/berkeley-softfloat-3 
tests/fp/berkeley-testfloat-3"
 sub_deinit=""
 
diff --git a/scripts/meson-buildoptions.sh b/scripts/meson-buildoptions.sh
index 1e26f4571e..dcfecb69ad 100644
--- a/scripts/meson-buildoptions.sh
+++ b/scripts/meson-buildoptions.sh
@@ -23,8 +23,6 @@ meson_options_help() {
   printf "%s\n" '  --enable-qom-cast-debug  cast debugging support'
   printf "%s\n" '  --enable-rng-none        dummy RNG, avoid using 
/dev/(u)random and'
   printf "%s\n" '                           getrandom()'
-  printf "%s\n" '  --enable-slirp[=CHOICE]  Whether and how to find the slirp 
library'
-  printf "%s\n" '                           (choices: 
auto/disabled/enabled/internal/system)'
   printf "%s\n" '  --enable-strip           Strip targets on install'
   printf "%s\n" '  --enable-tcg-interpreter TCG with bytecode interpreter 
(slow)'
   printf "%s\n" '  --enable-trace-backends=CHOICE'
@@ -103,6 +101,7 @@ meson_options_help() {
   printf "%s\n" '  sdl-image       SDL Image support for icons'
   printf "%s\n" '  seccomp         seccomp support'
   printf "%s\n" '  selinux         SELinux support in qemu-nbd'
+  printf "%s\n" '  slirp           libslirp user mode network backend support'
   printf "%s\n" '  slirp-smbd      use smbd (at path --smbd=*) in slirp 
networking'
   printf "%s\n" '  smartcard       CA smartcard emulation support'
   printf "%s\n" '  snappy          snappy compression support'
@@ -303,7 +302,6 @@ _meson_option_parse() {
     --disable-selinux) printf "%s" -Dselinux=disabled ;;
     --enable-slirp) printf "%s" -Dslirp=enabled ;;
     --disable-slirp) printf "%s" -Dslirp=disabled ;;
-    --enable-slirp=*) quote_sh "-Dslirp=$2" ;;
     --enable-slirp-smbd) printf "%s" -Dslirp_smbd=enabled ;;
     --disable-slirp-smbd) printf "%s" -Dslirp_smbd=disabled ;;
     --enable-smartcard) printf "%s" -Dsmartcard=enabled ;;
diff --git a/slirp b/slirp
deleted file mode 160000
index a88d9ace23..0000000000
--- a/slirp
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit a88d9ace234a24ce1c17189642ef9104799425e0
-- 
2.27.0