From 7f928a6573654de060b9bdad1da09697b4212a25 Mon Sep 17 00:00:00 2001
From: Emery Hemingway <ehmry@posteo.net>
Date: Thu, 21 Jun 2018 09:34:11 +0200
Subject: [PATCH] LxIP "peek" file

Add a control file for peeking at socket buffers.

Ref #2875
---
 repos/dde_linux/src/lib/vfs/lxip/vfs.cc | 60 ++++++++++++++++++++++++-
 1 file changed, 59 insertions(+), 1 deletion(-)

diff --git a/repos/dde_linux/src/lib/vfs/lxip/vfs.cc b/repos/dde_linux/src/lib/vfs/lxip/vfs.cc
index 5af3632f8..f811bf473 100644
--- a/repos/dde_linux/src/lib/vfs/lxip/vfs.cc
+++ b/repos/dde_linux/src/lib/vfs/lxip/vfs.cc
@@ -129,6 +129,7 @@ namespace Vfs {
 	class Lxip_listen_file;
 	class Lxip_local_file;
 	class Lxip_remote_file;
+	class Lxip_peek_file;
 
 	class Lxip_socket_dir;
 	struct Lxip_socket_handle;
@@ -521,6 +522,52 @@ class Vfs::Lxip_data_file final : public Vfs::Lxip_file
 };
 
 
+class Vfs::Lxip_peek_file final : public Vfs::Lxip_file
+{
+	public:
+
+		Lxip_peek_file(Lxip::Socket_dir &p, Linux::socket &s)
+		: Lxip_file(p, s, "peek") { }
+
+		/********************
+		 ** File interface **
+		 ********************/
+
+		bool poll() override
+		{
+			/* can always peek */
+			return true;
+		}
+
+		Lxip::ssize_t write(Lxip_vfs_file_handle&,
+		                    char const *, Genode::size_t,
+		                    file_size) override
+		{
+			return -1;
+		}
+
+		Lxip::ssize_t read(Lxip_vfs_file_handle &handle,
+		                   char *dst, Genode::size_t len,
+		                   file_size /* ignored */) override
+		{
+			using namespace Linux;
+
+			if (!_sock_valid()) return -1;
+
+			iovec iov { dst, len };
+
+			msghdr msg = create_msghdr(nullptr, 0, len, &iov);
+
+			Lxip::ssize_t ret = _sock.ops->recvmsg(&_sock, &msg, len, MSG_DONTWAIT|MSG_PEEK);
+
+			if (ret == -EAGAIN)
+				return 0;
+
+			return ret;
+		}
+};
+
+
 class Vfs::Lxip_bind_file final : public Vfs::Lxip_file
 {
 	private:
@@ -939,7 +986,8 @@ class Vfs::Lxip_socket_dir final : public Lxip::Socket_dir
 
 		enum {
 			ACCEPT_NODE, BIND_NODE, CONNECT_NODE,
-			DATA_NODE, LOCAL_NODE, LISTEN_NODE, REMOTE_NODE,
+			DATA_NODE, PEEK_NODE,
+			LOCAL_NODE, LISTEN_NODE, REMOTE_NODE,
 			ACCEPT_SOCKET_NODE,
 			MAX_FILES
 		};
@@ -965,6 +1013,7 @@ class Vfs::Lxip_socket_dir final : public Lxip::Socket_dir
 		Lxip_bind_file    _bind_file    { *this, _sock };
 		Lxip_connect_file _connect_file { *this, _sock };
 		Lxip_data_file    _data_file    { *this, _sock };
+		Lxip_peek_file    _peek_file    { *this, _sock };
 		Lxip_listen_file  _listen_file  { *this, _sock };
 		Lxip_local_file   _local_file   { *this, _sock };
 		Lxip_remote_file  _remote_file  { *this, _sock };
@@ -1001,6 +1050,7 @@ class Vfs::Lxip_socket_dir final : public Lxip::Socket_dir
 			_files[BIND_NODE]    = &_bind_file;
 			_files[CONNECT_NODE] = &_connect_file;
 			_files[DATA_NODE]    = &_data_file;
+			_files[PEEK_NODE]    = &_peek_file;
 			_files[LOCAL_NODE]   = &_local_file;
 			_files[REMOTE_NODE]  = &_remote_file;
 		}
@@ -1011,6 +1061,7 @@ class Vfs::Lxip_socket_dir final : public Lxip::Socket_dir
 			_bind_file.dissolve_handles();
 			_connect_file.dissolve_handles();
 			_data_file.dissolve_handles();
+			_peek_file.dissolve_handles();
 			_listen_file.dissolve_handles();
 			_local_file.dissolve_handles();
 			_remote_file.dissolve_handles();
@@ -1781,6 +1832,13 @@ class Vfs::Lxip_file_system : public Vfs::File_system,
 				return STAT_OK;
 			}
 
+			if (dynamic_cast<Lxip_peek_file*>(node)) {
+				out.type = Node_type::CONTINUOUS_FILE;
+				out.rwx  = Node_rwx::rw();
+				out.size = 0;
+				return STAT_OK;
+			}
+
 			if (dynamic_cast<Vfs::File*>(node)) {
 				out.type = Node_type::TRANSACTIONAL_FILE;
 				out.rwx  = Node_rwx::rw();