1 files changed, 124 insertions, 0 deletions
diff --git a/src/socket.c b/src/socket.c
new file mode 100644
index 0000000..45f4053
--- /dev/null
+++ b/src/socket.c
@@ -0,0 +1,124 @@
+/*
+ *	Socket-related functions
+ *	Copyright Jan Engelhardt, 2021
+ *
+ *	This file is part of libHX. libHX is free software; you can
+ *	redistribute it and/or modify it under the terms of the GNU Lesser
+ *	General Public License as published by the Free Software Foundation;
+ *	either version 2.1 or (at your option) any later version.
+ */
+#ifdef HAVE_CONFIG_H
+#	include "config.h"
+#endif
+#include <errno.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <string.h>
+#ifdef _WIN32
+#	include <ws2tcpip.h>
+#else
+#	include <sys/socket.h>
+#	include <netdb.h>
+#endif
+#include <libHX/proc.h>
+#include <libHX/socket.h>
+#include "internal.h"
+#ifdef _WIN32
+#	define STUPIDWIN(x) reinterpret_cast(char *, (x))
+#else
+#	define STUPIDWIN(x) (x)
+#endif
+#if defined(__sunos__) && !defined(SO_PROTOCOL)
+#	define SO_PROTOCOL SO_PROTOTYPE
+#endif
+
+static int try_sk_from_env(int fd, const struct addrinfo *ai, const char *intf)
+{
+	int value = 0;
+	socklen_t optlen = sizeof(value);
+	int ret = getsockopt(fd, SOL_SOCKET, SO_ACCEPTCONN, STUPIDWIN(&value), &optlen);
+	if (ret < 0 && errno != ENOPROTOOPT)
+		/*
+		 * E.g. OpenBSD's getsockopt does not recognize this - even
+		 * though the flag with the same name exists and is known.
+		 */
+		return -1;
+	if (ret == 0 && value == 0)
+		return -1;
+#ifdef _WIN32
+	WSAPROTOCOL_INFO protinfo;
+	optlen = sizeof(protinfo);
+	ret = getsockopt(fd, SOL_SOCKET, SO_PROTOCOL_INFO, STUPIDWIN(&protinfo), &optlen);
+	if (ret < 0 || protinfo.iAddressFamily != ai->ai_family ||
+	    protinfo.iSocketType != ai->ai_socktype ||
+	    protinfo.iProtocol != ai->ai_protocol)
+		return -1;
+#else
+	optlen = sizeof(value);
+	ret = getsockopt(fd, SOL_SOCKET, SO_DOMAIN, &value, &optlen);
+	if (ret < 0 || value != ai->ai_family)
+		return -1;
+	optlen = sizeof(value);
+	ret = getsockopt(fd, SOL_SOCKET, SO_TYPE, &value, &optlen);
+	if (ret < 0 || value != ai->ai_socktype)
+		return -1;
+	optlen = sizeof(value);
+	ret = getsockopt(fd, SOL_SOCKET, SO_PROTOCOL, &value, &optlen);
+	if (ret < 0 || value != ai->ai_protocol)
+		return -1;
+#endif
+	struct sockaddr_storage addr;
+	memset(&addr, 0, sizeof(addr));
+	optlen = sizeof(addr);
+	ret = getsockname(fd, (struct sockaddr *)&addr, &optlen);
+	if (ret < 0)
+		return -1;
+	if (sizeof(addr) < optlen)
+		optlen = sizeof(addr);
+	if (optlen != ai->ai_addrlen || memcmp(&addr, ai->ai_addr, optlen) != 0)
+		return -1;
+	if (intf == nullptr)
+		return fd;
+#ifdef SO_BINDTODEVICE
+	char ifname[32];
+	optlen = sizeof(ifname);
+	ret = getsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE, ifname, &optlen);
+	if (ret < 0)
+		return -1;
+	else if (optlen < sizeof(ifname))
+		ifname[optlen] = '\0';
+	else
+		ifname[sizeof(ifname)-1] = '\0';
+	if (strcmp(intf, ifname) != 0)
+		return -1;
+#endif
+	return fd;
+}
+
+EXPORT_SYMBOL int HX_socket_from_env(const struct addrinfo *ai, const char *intf)
+{
+	int top_fd;
+	const char *env_limit = getenv("LISTEN_FDS");
+	if (env_limit != nullptr) {
+		long x = strtol(env_limit, nullptr, 0);
+		if (x > INT_MAX - 3)
+			x = INT_MAX - 3;
+		top_fd = 3 + x;
+	} else {
+		env_limit = getenv("HX_LISTEN_TOP_FD");
+		long x;
+		if (env_limit != nullptr) {
+			x = strtol(env_limit, nullptr, 0);
+			if (x > INT_MAX)
+				x = INT_MAX;
+		} else {
+			x = HXproc_top_fd();
+		}
+		top_fd = x;
+	}
+	for (int fd = 3; fd < top_fd; ++fd)
+		if (try_sk_from_env(fd, ai, intf) == fd)
+			return fd;
+	errno = ENOENT;
+	return -1;
+}