ueventd: allow configuring SO_RCVBUF(FORCE) for the ueventd socket

Some configurations won't allow ueventd to have CAP_NET_ADMIN, so the
new default size of 16M is not possible for those.  Those
configurations also won't need such a large buffer size, so this
change allows devices to customize the SO_RCVBUF(FORCE) size for the
uevent socket.

This is done by adding the line 'uevent_socket_rcvbuf_size <size>' to
your device's ueventd.rc file.  <size> is specified as a byte count,
for example '16M' is 16MiB.

The last parsed uevent_socket_rcvbuf_size line is the one that is
used.

Bug: 120485624
Test: boot sailfish
Test: ueventd unit tests
Change-Id: If8123b92ca8a9b089ad50318caada2f21bc94707
diff --git a/init/ueventd_parser.cpp b/init/ueventd_parser.cpp
index 677938e..aac3fe5 100644
--- a/init/ueventd_parser.cpp
+++ b/init/ueventd_parser.cpp
@@ -19,9 +19,13 @@
 #include <grp.h>
 #include <pwd.h>
 
+#include <android-base/parseint.h>
+
 #include "keyword_map.h"
 #include "parser.h"
 
+using android::base::ParseByteCount;
+
 namespace android {
 namespace init {
 
@@ -101,6 +105,22 @@
     return Success();
 }
 
+Result<Success> ParseUeventSocketRcvbufSizeLine(std::vector<std::string>&& args,
+                                                size_t* uevent_socket_rcvbuf_size) {
+    if (args.size() != 2) {
+        return Error() << "uevent_socket_rcvbuf_size lines take exactly one parameter";
+    }
+
+    size_t parsed_size;
+    if (!ParseByteCount(args[1], &parsed_size)) {
+        return Error() << "could not parse size '" << args[1] << "' for uevent_socket_rcvbuf_line";
+    }
+
+    *uevent_socket_rcvbuf_size = parsed_size;
+
+    return Success();
+}
+
 class SubsystemParser : public SectionParser {
   public:
     SubsystemParser(std::vector<Subsystem>* subsystems) : subsystems_(subsystems) {}
@@ -202,6 +222,9 @@
     parser.AddSingleLineParser("modalias_handling",
                                std::bind(ParseModaliasHandlingLine, _1,
                                          &ueventd_configuration.enable_modalias_handling));
+    parser.AddSingleLineParser("uevent_socket_rcvbuf_size",
+                               std::bind(ParseUeventSocketRcvbufSizeLine, _1,
+                                         &ueventd_configuration.uevent_socket_rcvbuf_size));
 
     for (const auto& config : configs) {
         parser.ParseConfig(config);