P2PServer: prefer DNS TXT records to load seed nodes

CMakeLists.txt

@@ -129,7 +129,7 @@ if (WITH_UPNP)
 endif()
 
 if (WIN32)
-	set(LIBS ${LIBS} ws2_32 iphlpapi userenv psapi)
+	set(LIBS ${LIBS} ws2_32 iphlpapi userenv psapi dnsapi)
 	if (CMAKE_CXX_COMPILER_ID MATCHES GNU)
 		set(LIBS ${LIBS} bcrypt)
 	endif()
@@ -193,14 +193,60 @@ endif()
 
 add_definitions(/DZMQ_STATIC)
 
-set(CMAKE_REQUIRED_FLAGS "${GENERAL_FLAGS}")
-
 include(CheckCXXSourceCompiles)
 
 check_cxx_source_compiles("int main(){ return __builtin_clzll(1);}" HAVE_BUILTIN_CLZLL)
 check_cxx_source_compiles("#include <intrin.h>\n#pragma intrinsic(_BitScanReverse64)\nint main(){unsigned long r;_BitScanReverse64(&r,1);return r;}" HAVE_BITSCANREVERSE64)
 check_cxx_source_compiles("#include <sched.h>\nint main(){sched_param param;return sched_setscheduler(0, SCHED_IDLE, &param);}" HAVE_SCHED)
 
+include(CheckCSourceCompiles)
+
+set(CMAKE_REQUIRED_LIBRARIES "resolv")
+
+check_c_source_compiles("
+#include <arpa/nameser.h>
+#include <resolv.h>
+#include <stdio.h>
+#include <memory.h>
+
+int main(int argc, char* argv[])
+{
+	if (argc < 2) {
+		return 1;
+	}
+
+	res_init();
+
+	uint8_t answer[4096];
+	const int anslen = res_query(argv[1], ns_c_in, ns_t_txt, answer, sizeof(answer));
+
+	if (anslen > (int) sizeof(answer)) {
+		return 1;
+	}
+
+	ns_msg handle;
+	ns_initparse(answer, anslen, &handle);
+
+	for (int rrnum = 0, n = ns_msg_count(handle, ns_s_an); rrnum < n; ++rrnum) {
+		ns_rr rr;
+		if ((ns_parserr(&handle, ns_s_an, rrnum, &rr) == 0) && (ns_rr_type(rr) == ns_t_txt)) {
+			const uint8_t* data = ns_rr_rdata(rr);
+
+			int len = ns_rr_rdlen(rr) - 1;
+			if (len > data[0]) len = data[0];
+
+			char buf[256];
+			memcpy(buf, data + 1, len);
+			buf[len] = 0;
+			puts(buf);
+		}
+	}
+
+	return 0;
+}" HAVE_RES_QUERY)
+
+set(CMAKE_REQUIRED_LIBRARIES)
+
 if (HAVE_BUILTIN_CLZLL)
 	add_definitions(/DHAVE_BUILTIN_CLZLL)
 endif()
@@ -213,6 +259,11 @@ if (HAVE_SCHED)
 	add_definitions(/DHAVE_SCHED)
 endif()
 
+if (HAVE_RES_QUERY)
+	add_definitions(/DHAVE_RES_QUERY)
+	set(LIBS ${LIBS} resolv)
+endif()
+
 add_executable(${CMAKE_PROJECT_NAME} ${HEADERS} ${SOURCES})
 
 if (STATIC_BINARY OR STATIC_LIBS)
@@ -231,7 +282,7 @@ if (STATIC_BINARY OR STATIC_LIBS)
 	endif()
 
 	if (WIN32)
-		set(STATIC_LIBS ${STATIC_LIBS} ws2_32 iphlpapi userenv psapi wldap32)
+		set(STATIC_LIBS ${STATIC_LIBS} ws2_32 iphlpapi userenv psapi dnsapi)
 		if (CMAKE_CXX_COMPILER_ID MATCHES GNU)
 			set(STATIC_LIBS ${STATIC_LIBS} bcrypt)
 		endif()
@@ -246,6 +297,10 @@ if (STATIC_BINARY OR STATIC_LIBS)
 		set(STATIC_LIBS ${STATIC_LIBS} pthread)
 	endif()
 
+	if (HAVE_RES_QUERY)
+		set(STATIC_LIBS ${STATIC_LIBS} resolv)
+	endif()
+
 	target_link_libraries(${CMAKE_PROJECT_NAME}
 		"${CMAKE_SOURCE_DIR}/external/src/libzmq/build/lib/libzmq.a"
 		"${CMAKE_SOURCE_DIR}/external/src/libuv/build/libuv_a.a"

src/p2p_server.cpp

@@ -31,6 +31,13 @@
 #include <fstream>
 #include <numeric>
 
+#ifdef _WIN32
+#include <WinDNS.h>
+#elif defined(HAVE_RES_QUERY)
+#include <arpa/nameser.h>
+#include <resolv.h>
+#endif
+
 static constexpr char log_category_prefix[] = "P2PServer ";
 static constexpr char saved_peer_list_file_name[] = "p2pool_peers.txt";
 static const char* seed_nodes[] = { "seeds.p2pool.io", ""};
@@ -131,6 +138,10 @@ P2PServer::P2PServer(p2pool* pool)
 		PANIC_STOP();
 	}
 
+#if !defined(_WIN32) && defined(HAVE_RES_QUERY)
+	res_init();
+#endif
+
 	load_peer_list();
 	start_listening(params.m_p2pAddresses, params.m_upnp);
 }
@@ -488,6 +499,51 @@ void P2PServer::load_peer_list()
 		for (size_t i = 0; nodes[i][0]; ++i) {
 			LOGINFO(4, "loading peers from " << nodes[i]);
 
+			// Prefer DNS TXT records
+#ifdef _WIN32
+			PDNS_RECORD pQueryResults;
+			if (DnsQuery(nodes[i], DNS_TYPE_TEXT, DNS_QUERY_STANDARD, NULL, &pQueryResults, NULL) == 0) {
+				for (PDNS_RECORD p = pQueryResults; p; p = p->pNext) {
+					for (size_t j = 0; j < p->Data.TXT.dwStringCount; ++j) {
+						if (!saved_list.empty()) {
+							saved_list += ',';
+						}
+						LOGINFO(4, "added " << p->Data.TXT.pStringArray[j] << " from " << nodes[i]);
+						saved_list += p->Data.TXT.pStringArray[j];
+					}
+				}
+				DnsRecordListFree(pQueryResults, DnsFreeRecordList);
+				continue;
+			}
+#elif defined(HAVE_RES_QUERY)
+			uint8_t answer[4096];
+			const int anslen = res_query(nodes[i], ns_c_in, ns_t_txt, answer, sizeof(answer));
+
+			if ((0 < anslen) && (anslen < static_cast<int>(sizeof(answer)))) {
+				ns_msg handle;
+				if (ns_initparse(answer, anslen, &handle) == 0) {
+					for (int rrnum = 0, n = ns_msg_count(handle, ns_s_an); rrnum < n; ++rrnum) {
+						ns_rr rr;
+						if ((ns_parserr(&handle, ns_s_an, rrnum, &rr) == 0) && (ns_rr_type(rr) == ns_t_txt)) {
+							const uint8_t* data = ns_rr_rdata(rr);
+
+							const int len = std::min<int>(ns_rr_rdlen(rr) - 1, *data);
+							++data;
+
+							if (!saved_list.empty()) {
+								saved_list += ',';
+							}
+
+							const char* c = reinterpret_cast<const char*>(data);
+							LOGINFO(4, "added " << log::const_buf(c, len) << " from " << nodes[i]);
+							saved_list.append(c, len);
+						}
+					}
+					continue;
+				}
+			}
+#endif
+
 			addrinfo hints{};
 			hints.ai_family = AF_UNSPEC;
 			hints.ai_socktype = SOCK_STREAM;

src/tcp_server.cpp

@@ -113,7 +113,7 @@ void TCPServer::parse_address_list_internal(const std::string& address_list, Cal
 				}
 			}
 
-			const int port = atoi(address.substr(k2 + 1).c_str());
+			const int port = strtol(address.substr(k2 + 1).c_str(), nullptr, 10);
 			if ((port > 0) && (port < 65536)) {
 				callback(is_v6, address, ip, port);
 			}

tests/CMakeLists.txt

@@ -95,7 +95,7 @@ include_directories(src)
 include_directories(googletest/googletest/include)
 
 if (WIN32)
-	set(LIBS ${LIBS} ws2_32 iphlpapi userenv psapi wldap32)
+	set(LIBS ${LIBS} ws2_32 iphlpapi userenv psapi dnsapi)
 	if (CMAKE_CXX_COMPILER_ID MATCHES GNU)
 		set(LIBS ${LIBS} bcrypt)
 	endif()