Add utility to determine if ip is local external (#8)

* Added Utility to termine whether ipv4 is external local

* Added gsl to conanfile

* Added recognizing ipv4 link local addresses

* File NetlinkCalls added

Co-authored-by: Hubert Parzych <hubert.parzych@dynatrace.com>

CMakeLists.txt

@@ -77,7 +77,14 @@ endif(NOT TARGET fmt)
 
 find_package(Protobuf REQUIRED)
 
+
+find_package(Microsoft.GSL REQUIRED)
+if(Microsoft.GSL_FOUND)
+	include_directories(${Microsoft.GSL_INCLUDE_DIRS})
+endif()
+
 set(INSTALL_GTEST OFF CACHE BOOL "Disable installation of googletest" FORCE)
+
 if(BUILD_TESTS OR BUILD_BPF_TESTS)
 	include(FetchContent)
 	FetchContent_Declare(googletest URL https://github.com/google/googletest/archive/03597a01ee50ed33e9dfd640b249b4be3799d395.zip)

conanfile.txt

@@ -1,6 +1,7 @@
 [requires]
 protobuf/3.21.9
 protobuf-c/1.4.1
+ms-gsl/4.0.0
 fmt/10.1.1
 spdlog/1.12.0
 gtest/1.14.0

libebpfdiscovery/CMakeLists.txt

@@ -3,6 +3,8 @@ list(
 	SOURCES
 	src/Config.cpp
 	src/Discovery.cpp
+	src/IpAddressChecker.cpp
+	src/NetlinkCalls.cpp
 	src/Session.cpp
 	src/StringFunctions.cpp
 )
@@ -11,6 +13,7 @@ set(TARGET ebpfdiscovery)
 add_library(${TARGET} STATIC ${SOURCES})
 
 target_include_directories(${TARGET} PRIVATE src PUBLIC headers)
+
 target_link_libraries(${TARGET} bpfload)
 target_link_libraries(${TARGET} ebpfdiscoveryshared)
 target_link_libraries(${TARGET} ebpfdiscoveryskel)
@@ -19,11 +22,11 @@ target_link_libraries(${TARGET} httpparser)
 target_link_libraries(${TARGET} ebpfdiscoveryproto)
 
 if(BUILD_TESTS)
-	list(APPEND TEST_SOURCES test/StringFunctionsTest.cpp test/LRUCacheTest.cpp)
+	list(APPEND TEST_SOURCES test/StringFunctionsTest.cpp test/LRUCacheTest.cpp test/IpAddressCheckerTest.cpp)
 	set(TEST_TARGET test${TARGET})
 
 	add_executable(${TEST_TARGET} ${TEST_SOURCES})
-	target_link_libraries(${TEST_TARGET} GTest::gtest_main ${TARGET})
+	target_link_libraries(${TEST_TARGET} GTest::gtest_main GTest::gmock_main ${TARGET})
 	target_include_directories(${TEST_TARGET} PRIVATE src)
 	gtest_discover_tests(${TEST_TARGET})
 endif()

libebpfdiscovery/headers/ebpfdiscovery/IpAddressChecker.h

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: Apache-2.0
+#pragma once
+#include "ebpfdiscovery/NetlinkCalls.h"
+#include <initializer_list>
+#include <vector>
+
+
+namespace ebpfdiscovery {
+
+using IPv4int = uint32_t;
+
+struct IpIfce {
+	std::vector<IPv4int> ip;
+	std::vector<IPv4int> broadcast;
+	uint32_t mask;
+	int index;
+	bool isLocalBridge;
+};
+
+class IpAddressChecker {
+	std::vector<IpIfce> interfaces;
+	std::vector<IpIfce>::iterator bridgeEnd = interfaces.end();
+	const NetlinkCalls& netlink;
+
+	bool readAllIpAddrs();
+	bool markLocalBridges();
+	bool isLoopback(const IpIfce&);
+	void addIpIfce(IpIfce&& ifce);
+	void markBridge(int idx);
+protected:
+	void moveBridges();
+public:
+	IpAddressChecker(const NetlinkCalls &calls);
+	IpAddressChecker(std::initializer_list<IpIfce> config, const NetlinkCalls &calls);
+	bool isAddressExternalLocal(IPv4int addr);
+	bool readNetworks();
+};
+} // namespace ebpfdiscovery
+

libebpfdiscovery/headers/ebpfdiscovery/NetlinkCalls.h

@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: Apache-2.0
+#pragma once
+#include <cstdint>
+#include <stddef.h>
+
+struct sockaddr_nl;
+
+namespace ebpfdiscovery {
+
+class NetlinkCalls {
+public:
+	virtual int sendIpAddrRequest(int fd, sockaddr_nl* dst, int domain) const;
+	virtual int sendBridgesRequest(int fd, sockaddr_nl* dst, int domain) const;
+	virtual int receive(int fd, sockaddr_nl* dst, void* buf, size_t len) const;
+};
+} // namespace ebpfdiscovery
+

libebpfdiscovery/src/IpAddressChecker.cpp

@@ -0,0 +1,199 @@
+// SPDX-License-Identifier: Apache-2.0
+#include "ebpfdiscovery/IpAddressChecker.h"
+
+#include <algorithm>
+#include <arpa/inet.h>
+#include <array>
+#include <cstring>
+#include <errno.h>
+#include <gsl/util>
+#include <iostream>
+#include <linux/rtnetlink.h>
+#include <string>
+#include <string_view>
+#include <unistd.h>
+
+static constexpr uint32_t BUFLEN{4096};
+static constexpr uint32_t IP_CLASS_C{0x0000a8c0}; // 192.168.*.*
+static constexpr uint32_t MASK_CLASS_C{0x0000ffff};
+static constexpr uint32_t IP_CLASS_B{0x000010ac}; // 172.16-31.*.*
+static constexpr uint32_t MASK_CLASS_B{0x0000f0ff};
+static constexpr uint32_t IP_CLASS_A{0x0000000a}; // 10.*.*.*
+static constexpr uint32_t MASK_CLASS_A{0x000000ff};
+static constexpr uint32_t IP_LINK_LOCAL{0x0000fea9}; // 169.254.*.*
+static constexpr uint32_t MASK_LINK_LOCAL{0x0000ffff};
+static constexpr uint32_t IP_LOOPBACK{0x0000007f}; // 127.0.*.*
+static constexpr uint32_t MASK_LOOPBACK{0x00ffffff};
+
+static void logErrorFromErrno(std::string_view prefix) {
+	std::cout << prefix << ": " << strerror(errno) << "\n";
+}
+
+static ebpfdiscovery::IpIfce parseIfceIPv4(void* data, size_t len) {
+	ebpfdiscovery::IpIfce ifce{};
+	ifaddrmsg* ifa = reinterpret_cast<ifaddrmsg*>(data);
+	ifce.index = ifa->ifa_index;
+	ifce.mask = htonl(-1 << (32 - ifa->ifa_prefixlen));
+	rtattr* rta = reinterpret_cast<rtattr*>(IFA_RTA(data));
+
+	for (; RTA_OK(rta, len); rta = RTA_NEXT(rta, len)) {
+		in_addr* addr = reinterpret_cast<in_addr*>(RTA_DATA(rta));
+
+		if (rta->rta_type == IFA_ADDRESS) {
+			ifce.ip.push_back(addr->s_addr);
+		}
+
+		if (rta->rta_type == IFA_BROADCAST) {
+			ifce.broadcast.push_back(addr->s_addr);
+		}
+	}
+
+	return ifce;
+}
+
+static ebpfdiscovery::IpIfce parseIfce(void* data, size_t len) {
+	if (reinterpret_cast<ifaddrmsg*>(data)->ifa_family != AF_INET) {
+		return {};
+	}
+
+	return parseIfceIPv4(data, len);
+}
+
+static int getIfIndex(void* data) {
+	ifinfomsg* ifa = reinterpret_cast<ifinfomsg*>(data);
+	return ifa->ifi_index;
+}
+
+namespace ebpfdiscovery {
+
+IpAddressChecker::IpAddressChecker(std::initializer_list<IpIfce> config, const NetlinkCalls &calls) :netlink(calls) {
+	interfaces.insert(interfaces.end(), config.begin(), config.end());
+}
+
+IpAddressChecker::IpAddressChecker(const NetlinkCalls &calls) :netlink(calls) {
+}
+
+bool IpAddressChecker::readNetworks() {
+	const bool ret = readAllIpAddrs();
+	if (markLocalBridges()) {
+		moveBridges();
+	} else {
+		bridgeEnd = interfaces.end();
+	}
+
+	return ret;
+}
+
+void IpAddressChecker::moveBridges() {
+	bridgeEnd = std::partition(interfaces.begin(), interfaces.end(), [](const auto& it) { return it.isLocalBridge; });
+}
+
+template <typename P>
+static uint32_t parseNlMsg(void* buf, size_t len, P parse) {
+	const nlmsghdr* nl = reinterpret_cast<nlmsghdr*>(buf);
+
+	for (; NLMSG_OK(nl, len) && nl->nlmsg_type != NLMSG_DONE; nl = NLMSG_NEXT(nl, len)) {
+		if (nl->nlmsg_type == NLMSG_ERROR) {
+			return -1;
+		}
+
+		if (nl->nlmsg_type == RTM_NEWADDR || nl->nlmsg_type == RTM_NEWLINK) {
+			parse(NLMSG_DATA(nl), IFA_PAYLOAD(nl));
+			continue;
+		}
+	}
+
+	return nl->nlmsg_type;
+}
+
+template <typename S, typename P, typename R>
+static bool handleNetlink(S send, R receive, P parse, int domain) {
+	int fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
+	if (fd < 0) {
+		logErrorFromErrno("socket");
+		return false;
+	}
+
+	auto const _ = gsl::finally([fd]() { ::close(fd); });
+	sockaddr_nl sa{};
+	sa.nl_family = AF_NETLINK;
+
+	int len = send(fd, &sa, domain);
+	if (len <= 0) {
+		logErrorFromErrno("send");
+		return false;
+	}
+
+	uint32_t nlMsgType;
+	do {
+		std::array<char, BUFLEN> buf{};
+		len = receive(fd, &sa, buf.data(), BUFLEN);
+		if (len <= 0) {
+			logErrorFromErrno("receive");
+			break;
+		}
+
+		nlMsgType = parseNlMsg(buf.data(), len, parse);
+	} while (nlMsgType != NLMSG_DONE && nlMsgType != NLMSG_ERROR);
+
+	return true;
+}
+
+bool IpAddressChecker::readAllIpAddrs() {
+	return handleNetlink(
+			[this](int fd, sockaddr_nl* sa, int domain) { return netlink.sendIpAddrRequest(fd, sa, AF_INET); },
+			[this](int fd, sockaddr_nl* dst, void* buf, size_t len) { return netlink.receive(fd, dst, buf, len); },
+			[this](void* buf, size_t len) { addIpIfce(parseIfce(buf, len)); }, AF_INET);
+}
+
+bool IpAddressChecker::markLocalBridges() {
+	return handleNetlink(
+			[this](int fd, sockaddr_nl* sa, int domain) { return netlink.sendBridgesRequest(fd, sa, AF_INET); },
+			[this](int fd, sockaddr_nl* dst, void* buf, size_t len) { return netlink.receive(fd, dst, buf, len); },
+			[this](void* buf, size_t len) { markBridge(getIfIndex(buf)); }, AF_INET);
+}
+
+void IpAddressChecker::addIpIfce(IpIfce&& ifce) {
+	if(!isLoopback(ifce)){
+		interfaces.push_back(ifce);
+	}
+}
+
+void IpAddressChecker::markBridge(int idx) {
+	auto ifc = std::find_if(interfaces.begin(), interfaces.end(), [idx](const auto& it) { return it.index == idx; });
+	if (ifc == interfaces.end()) {
+		return;
+	}
+
+	ifc->isLocalBridge = true;
+}
+
+bool IpAddressChecker::isLoopback(const IpIfce& ifce) {
+
+	return std::all_of(ifce.ip.begin(), ifce.ip.end(), [](const auto& ipv4) {
+		return ((ipv4 & MASK_LOOPBACK) == IP_LOOPBACK);
+	});
+}
+
+bool IpAddressChecker::isAddressExternalLocal(IPv4int addr) {
+	const bool isPublic = ((addr & MASK_CLASS_A) != IP_CLASS_A) && ((addr & MASK_CLASS_B) != IP_CLASS_B) && ((addr & MASK_CLASS_C) != IP_CLASS_C);
+
+	if (isPublic) {
+		return false;
+	}
+
+	if ((addr & MASK_LINK_LOCAL) == IP_LINK_LOCAL) {
+		return false;
+	}
+
+	const bool bridgeRelated = std::any_of(interfaces.begin(), bridgeEnd, [addr](const auto& it) {
+		return std::any_of(it.ip.begin(), it.ip.end(), [addr, mask = it.mask](const auto& ip) { return (addr & mask) == (ip & mask); });
+	});
+
+	if (bridgeRelated) {
+		return false;
+	}
+
+	return true;
+}
+} // namespace ebpfdiscovery

libebpfdiscovery/src/NetlinkCalls.cpp

@@ -0,0 +1,84 @@
+#include "ebpfdiscovery/NetlinkCalls.h"
+#include <arpa/inet.h>
+#include <array>
+#include <linux/rtnetlink.h>
+#include <net/if.h>
+#include <cstring>
+
+namespace ebpfdiscovery {
+
+static constexpr uint32_t BUFFLEN{4096};
+
+static void addNetlinkMsg(nlmsghdr* nh, int type, const void* data, int dataLen) {
+	struct rtattr* rta;
+	int rta_length = RTA_LENGTH(dataLen);
+
+	rta = reinterpret_cast<rtattr*>((char*)nh + NLMSG_ALIGN(nh->nlmsg_len));
+
+	rta->rta_type = type;
+	rta->rta_len = rta_length;
+	nh->nlmsg_len = NLMSG_ALIGN(nh->nlmsg_len) + RTA_ALIGN(rta_length);
+
+	memcpy(RTA_DATA(rta), data, dataLen);
+}
+
+int NetlinkCalls::sendIpAddrRequest(int fd, sockaddr_nl* dst, int domain) const {
+	std::array<char, BUFFLEN> buf{};
+
+	nlmsghdr* nl;
+	nl = reinterpret_cast<nlmsghdr*>(buf.data());
+	nl->nlmsg_len = NLMSG_LENGTH(sizeof(ifaddrmsg));
+	nl->nlmsg_type = RTM_GETADDR;
+	nl->nlmsg_flags = NLM_F_REQUEST | NLM_F_ROOT;
+
+	ifaddrmsg* ifa;
+	ifa = reinterpret_cast<ifaddrmsg*>(NLMSG_DATA(nl));
+	ifa->ifa_family = domain; // ipv4 or ipv6
+
+	iovec iov = {nl, nl->nlmsg_len};
+	msghdr msg = {dst, sizeof(*dst), &iov, 1, NULL, 0, 0};
+
+	return sendmsg(fd, &msg, 0);
+}
+
+int NetlinkCalls::sendBridgesRequest(int fd, sockaddr_nl* dst, int domain) const {
+	struct {
+		struct nlmsghdr n;
+		struct ifinfomsg i;
+		char _[1024]; // space for rtattr array
+	} r{};
+
+	const char* dev_type = "bridge";
+
+	r.n.nlmsg_len = NLMSG_LENGTH(sizeof(ifinfomsg));
+	r.n.nlmsg_type = RTM_GETLINK;
+	r.n.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
+	r.i.ifi_family = AF_PACKET;
+	r.n.nlmsg_pid = 0;
+	r.n.nlmsg_seq = 0;
+
+	rtattr* linkinfo = reinterpret_cast<rtattr*>((char*)&r.n + NLMSG_ALIGN(r.n.nlmsg_len));
+	addNetlinkMsg(&r.n, IFLA_LINKINFO, NULL, 0);
+	addNetlinkMsg(&r.n, IFLA_INFO_KIND, dev_type, strlen(dev_type) + 1);
+	linkinfo->rta_len = (int)(reinterpret_cast<char*>(&r.n) + NLMSG_ALIGN(r.n.nlmsg_len) - reinterpret_cast<char*>(linkinfo));
+
+	iovec iov = {&r.n, r.n.nlmsg_len};
+	msghdr msg = {dst, sizeof(*dst), &iov, 1, NULL, 0, 0};
+
+	return sendmsg(fd, &msg, 0);
+}
+
+int NetlinkCalls::receive(int fd, sockaddr_nl* dst, void* buf, size_t len) const {
+	iovec iov;
+	msghdr msg{};
+	iov.iov_base = buf;
+	iov.iov_len = len;
+
+	msg.msg_name = dst;
+	msg.msg_namelen = sizeof(*dst);
+	msg.msg_iov = &iov;
+	msg.msg_iovlen = 1;
+
+	return recvmsg(fd, &msg, 0);
+}
+} // namespace ebpfdiscovery