From 59ba39ae960714b31ef2c5aa4711ff21b5497c1f Mon Sep 17 00:00:00 2001
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Tue, 29 Jul 2014 04:31:29 +0200
Subject: [PATCH] Add new package libpacketmark, a LD_PRELOAD library to
 manipulate packet marks

---
 libs/libpacketmark/Makefile            | 34 +++++++++++++++
 libs/libpacketmark/src/Makefile        |  4 ++
 libs/libpacketmark/src/libpacketmark.c | 60 ++++++++++++++++++++++++++
 3 files changed, 98 insertions(+)
 create mode 100644 libs/libpacketmark/Makefile
 create mode 100644 libs/libpacketmark/src/Makefile
 create mode 100644 libs/libpacketmark/src/libpacketmark.c

diff --git a/libs/libpacketmark/Makefile b/libs/libpacketmark/Makefile
new file mode 100644
index 0000000..6e359a0
--- /dev/null
+++ b/libs/libpacketmark/Makefile
@@ -0,0 +1,34 @@
+include $(TOPDIR)/rules.mk
+
+PKG_NAME:=libpacketmark
+PKG_VERSION:=1
+
+PKG_BUILD_DIR := $(BUILD_DIR)/$(PKG_NAME)
+
+include $(INCLUDE_DIR)/package.mk
+
+define Package/libpacketmark
+  SECTION:=libs
+  CATEGORY:=Libraries
+  TITLE:=Set default packet mark via LD_PRELOAD
+  DEPENDS:=
+endef
+
+define Build/Prepare
+	mkdir -p $(PKG_BUILD_DIR)
+	$(CP) ./src/* $(PKG_BUILD_DIR)/
+endef
+
+define Build/Configure
+endef
+
+define Build/Compile
+	CFLAGS="$(TARGET_CFLAGS)" CPPFLAGS="$(TARGET_CPPFLAGS)" $(MAKE) -C $(PKG_BUILD_DIR) $(TARGET_CONFIGURE_OPTS)
+endef
+
+define Package/libpacketmark/install
+	$(INSTALL_DIR) $(1)/usr/lib
+	$(CP) $(PKG_BUILD_DIR)/libpacketmark.so $(1)/usr/lib/
+endef
+
+$(eval $(call BuildPackage,libpacketmark))
diff --git a/libs/libpacketmark/src/Makefile b/libs/libpacketmark/src/Makefile
new file mode 100644
index 0000000..40e0d35
--- /dev/null
+++ b/libs/libpacketmark/src/Makefile
@@ -0,0 +1,4 @@
+all: libpacketmark.so
+
+libpacketmark.so: libpacketmark.c
+	$(CC) $(CPPFLAGS) $(CFLAGS) $(LDFLAGS) -Wall -nostartfiles -shared -fPIC -o $@ $^ -ldl $(LDLIBS)
diff --git a/libs/libpacketmark/src/libpacketmark.c b/libs/libpacketmark/src/libpacketmark.c
new file mode 100644
index 0000000..4cc3fae
--- /dev/null
+++ b/libs/libpacketmark/src/libpacketmark.c
@@ -0,0 +1,60 @@
+/*
+  Copyright (c) 2014, Matthias Schiffer <mschiffer@universe-factory.net>
+  All rights reserved.
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions are met:
+
+    1. Redistributions of source code must retain the above copyright notice,
+       this list of conditions and the following disclaimer.
+    2. Redistributions in binary form must reproduce the above copyright notice,
+       this list of conditions and the following disclaimer in the documentation
+       and/or other materials provided with the distribution.
+
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+
+#define _GNU_SOURCE
+
+#include <dlfcn.h>
+#include <errno.h>
+#include <stdlib.h>
+
+#include <sys/types.h>
+#include <sys/socket.h>
+
+
+static int mark;
+static int (*socket_real)(int domain, int type, int protocol);
+
+
+void _init(void) {
+	const char *str = getenv("LIBPACKETMARK_MARK");
+	if (str)
+		mark = atoi(str);
+
+	socket_real = dlsym(RTLD_NEXT, "socket");
+}
+
+
+int socket(int domain, int type, int protocol) {
+	int fd = socket_real(domain, type, protocol);
+
+	if (fd >= 0) {
+		int errno_save = errno;
+		setsockopt(fd, SOL_SOCKET, SO_MARK, &mark, sizeof(mark));
+		errno = errno_save;
+	}
+
+	return fd;
+}