mdns: add mdns for local network routing

WORKSPACE.bazel

@@ -130,6 +130,15 @@ versioned_http_archive(
     version = "a4c1e3f7138c2e577376beb99f964cf71e1c8b1b",
 )
 
+versioned_http_archive(
+    name = "avahi",
+    build_file = "//bazel/third_party/avahi:avahi.BUILD",
+    sha256 = "060309d7a333d38d951bc27598c677af1796934dbd98e1024e7ad8de798fedda",
+    strip_prefix = "avahi-{version}",
+    url = "https://github.com/lathiat/avahi/releases/download/v{version}/avahi-{version}.tar.gz",
+    version = "0.8",
+)
+
 versioned_http_archive(
     name = "bazel_gazelle",
     sha256 = "efbbba6ac1a4fd342d5122cbdfdb82aeb2cf2862e35022c752eaddffada7c3f3",
@@ -154,6 +163,15 @@ versioned_http_archive(
     version = "7.85.0",
 )
 
+versioned_http_archive(
+    name = "dbus",
+    build_file = "//bazel/third_party/dbus:dbus.BUILD",
+    sha256 = "a6bd5bac5cf19f0c3c594bdae2565a095696980a683a0ef37cb6212e093bde35",
+    strip_prefix = "dbus-{version}",
+    url = "https://dbus.freedesktop.org/releases/dbus/dbus-{version}.tar.xz",
+    version = "1.14.8",
+)
+
 versioned_http_archive(
     name = "ed25519",
     build_file = "//bazel/third_party/ed25519:ed25519.BUILD",
@@ -163,6 +181,16 @@ versioned_http_archive(
     version = "7fa6712ef5d581a6981ec2b08ee623314cd1d1c4",
 )
 
+versioned_http_archive(
+    name = "expat",
+    build_file = "//bazel/third_party/expat:expat.BUILD",
+    strip_prefix = "expat-{version}",
+    sha256 = "ef2420f0232c087801abf705e89ae65f6257df6b7931d37846a193ef2e8cdcbe",
+    # TODO: fix the R_2_5_0 nonsense
+    url = "https://github.com/libexpat/libexpat/releases/download/R_2_5_0/expat-{version}.tar.xz",
+    version = "2.5.0",
+)
+
 versioned_http_archive(
     name = "gmp",
     build_file = "//bazel/third_party/gmp:gmp.BUILD",

bazel/third_party/avahi/avahi.BUILD

@@ -0,0 +1,30 @@
+load("@rules_foreign_cc//foreign_cc:defs.bzl", "configure_make")
+
+filegroup(
+    name = "all",
+    srcs = glob(["**"]),
+)
+
+cc_library(
+    name = "dns-sd",
+    hdrs = ["dns_sd.h"],
+    visibility = ["//visibility:public"],
+)
+
+configure_make(
+    name = "avahi",
+    args = select({
+        "@platforms//os:macos": ["--jobs=`sysctl -n hw.logicalcpu`"],
+        "//conditions:default": ["--jobs=`nproc`"],
+    }),
+    configure_options = ["--with-dbus-system-address='unix:path=/var/run/dbus/system_bus_socket' --with-xml=none --disable-libevent --disable-glib --disable-gobject --disable-gdbm --disable-qt3 --disable-qt4 --disable-qt5 --disable-gtk --disable-gtk3 --disable-mono --disable-monodoc --disable-python --disable-libdaemon --enable-compat-libdns_sd --disable-rpath"],
+    lib_source = ":all",
+    # out_include_dir = "avahi-compat-libdns_sd",
+    deps = ["@dbus"],
+    configure_in_place = True,
+    autogen = True,
+    autoconf = True,
+    autogen_command = "bootstrap.sh",
+    out_static_libs = ["libdns_sd.a", "libavahi-client.a", "libavahi-common.a"],
+    visibility = ["//visibility:public"],
+)

bazel/third_party/dbus/dbus.BUILD

@@ -0,0 +1,21 @@
+load("@rules_foreign_cc//foreign_cc:defs.bzl", "configure_make")
+
+filegroup(
+    name = "all",
+    srcs = glob(["**"]),
+)
+
+configure_make(
+    name = "dbus",
+    lib_name = "libdbus-1",
+    args = select({
+        "@platforms//os:macos": ["--jobs=`sysctl -n hw.logicalcpu`"],
+        "//conditions:default": ["--jobs=`nproc`"],
+    }),
+    copts = ["-O3"],
+    lib_source = ":all",
+    configure_in_place = True,
+    deps = ["@expat"],
+    alwayslink = True,
+    visibility = ["//visibility:public"],
+)

bazel/third_party/expat/expat.BUILD

@@ -0,0 +1,20 @@
+load("@rules_foreign_cc//foreign_cc:defs.bzl", "configure_make")
+
+filegroup(
+    name = "all",
+    srcs = glob(["**"]),
+)
+
+configure_make(
+    name = "expat",
+    args = select({
+        "@platforms//os:macos": ["--jobs=`sysctl -n hw.logicalcpu`"],
+        "//conditions:default": ["--jobs=`nproc`"],
+    }),
+    # configure_options = ["--with-xml=none --disable-libevent --disable-glib --disable-gobject --disable-gdbm --disable-qt3 --disable-qt4 --disable-qt5 --disable-gtk --disable-gtk3 --disable-mono --disable-monodoc --disable-python --enable-compat-libdns_sd"],
+    copts = ["-O3"],
+    lib_source = ":all",
+    # deps = ["@dbus"],
+    out_static_libs = ["libexpat.a"],
+    visibility = ["//visibility:public"],
+)

pkg/c3/motes.h

@@ -308,6 +308,7 @@
 #   define c3__deep   c3_s4('d','e','e','p')
 #   define c3__defn   c3_s4('d','e','f','n')
 #   define c3__del    c3_s3('d','e','l')
+#   define c3__dear   c3_s4('d','e','a','r')
 #   define c3__delc   c3_s4('d','e','l','c')
 #   define c3__delt   c3_s4('d','e','l','t')
 #   define c3__dept   c3_s4('d','e','p','t')

pkg/vere/BUILD.bazel

@@ -119,7 +119,12 @@ vere_library(
     hdrs = [
         "db/lmdb.h",
         "vere.h",
-    ],
+    ] + select({
+        "@platforms//os:macos": [],
+        "@platforms//os:linux": [
+            "dns_sd.h",
+        ],
+        }),
     includes = ["."],
     linkstatic = True,
     visibility = ["//pkg:__subpackages__"],
@@ -133,7 +138,12 @@ vere_library(
         "@lmdb",
         "@openssl",
         "@uv",
-    ],
+    ] + select({
+        "@platforms//os:macos": [],
+        "@platforms//os:linux": [
+            "@avahi",
+        ],
+        })
 )
 
 #