[NETD-BPF#1] Move libnetdutils to framework/libs/net/...

libnetdutils is referenced by netd.c and TrafficController.cpp, which
are going to be mainlined. Therefore, move libnetdutils to a common
place where both mainline module and platform code (Netd) can refer to.

Bug: 202086915
Test: build; flash; cd system/netd; atest
No-Typo-Check: Clean code move with no other changes.
BYPASS_INCLUSIVE_LANGUAGE_REASON=Clean code move with no other changes.

Merged-In: I645bfe35f6543149c9a9f894cd4158d27a481abe
Change-Id: I645bfe35f6543149c9a9f894cd4158d27a481abe
diff --git a/staticlibs/netd/libnetdutils/Syscalls.cpp b/staticlibs/netd/libnetdutils/Syscalls.cpp
new file mode 100644
index 0000000..9f653f7
--- /dev/null
+++ b/staticlibs/netd/libnetdutils/Syscalls.cpp
@@ -0,0 +1,265 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "netdutils/Syscalls.h"
+
+#include <atomic>
+#include <type_traits>
+#include <utility>
+
+namespace android {
+namespace netdutils {
+namespace {
+
+// Retry syscall fn as long as it returns -1 with errno == EINTR
+template <typename FnT, typename... Params>
+typename std::result_of<FnT(Params...)>::type syscallRetry(FnT fn, Params&&... params) {
+    auto rv = fn(std::forward<Params>(params)...);
+    while ((rv == -1) && (errno == EINTR)) {
+        rv = fn(std::forward<Params>(params)...);
+    }
+    return rv;
+}
+
+}  // namespace
+
+// Production implementation of Syscalls that forwards to libc syscalls.
+class RealSyscalls final : public Syscalls {
+  public:
+    ~RealSyscalls() override = default;
+
+    StatusOr<UniqueFd> open(const std::string& pathname, int flags, mode_t mode) const override {
+        UniqueFd fd(::open(pathname.c_str(), flags, mode));
+        if (!isWellFormed(fd)) {
+            return statusFromErrno(errno, "open(\"" + pathname + "\"...) failed");
+        }
+        return fd;
+    }
+
+    StatusOr<UniqueFd> socket(int domain, int type, int protocol) const override {
+        UniqueFd sock(::socket(domain, type, protocol));
+        if (!isWellFormed(sock)) {
+            return statusFromErrno(errno, "socket() failed");
+        }
+        return sock;
+    }
+
+    Status getsockname(Fd sock, sockaddr* addr, socklen_t* addrlen) const override {
+        auto rv = ::getsockname(sock.get(), addr, addrlen);
+        if (rv == -1) {
+            return statusFromErrno(errno, "getsockname() failed");
+        }
+        return status::ok;
+    }
+
+    Status getsockopt(Fd sock, int level, int optname, void* optval,
+                      socklen_t* optlen) const override {
+        auto rv = ::getsockopt(sock.get(), level, optname, optval, optlen);
+        if (rv == -1) {
+            return statusFromErrno(errno, "getsockopt() failed");
+        }
+        return status::ok;
+    }
+
+    Status setsockopt(Fd sock, int level, int optname, const void* optval,
+                      socklen_t optlen) const override {
+        auto rv = ::setsockopt(sock.get(), level, optname, optval, optlen);
+        if (rv == -1) {
+            return statusFromErrno(errno, "setsockopt() failed");
+        }
+        return status::ok;
+    }
+
+    Status bind(Fd sock, const sockaddr* addr, socklen_t addrlen) const override {
+        auto rv = ::bind(sock.get(), addr, addrlen);
+        if (rv == -1) {
+            return statusFromErrno(errno, "bind() failed");
+        }
+        return status::ok;
+    }
+
+    Status connect(Fd sock, const sockaddr* addr, socklen_t addrlen) const override {
+        auto rv = syscallRetry(::connect, sock.get(), addr, addrlen);
+        if (rv == -1) {
+            return statusFromErrno(errno, "connect() failed");
+        }
+        return status::ok;
+    }
+
+    StatusOr<ifreq> ioctl(Fd sock, unsigned long request, ifreq* ifr) const override {
+        auto rv = ::ioctl(sock.get(), request, ifr);
+        if (rv == -1) {
+            return statusFromErrno(errno, "ioctl() failed");
+        }
+        return *ifr;
+    }
+
+    StatusOr<UniqueFd> eventfd(unsigned int initval, int flags) const override {
+        UniqueFd fd(::eventfd(initval, flags));
+        if (!isWellFormed(fd)) {
+            return statusFromErrno(errno, "eventfd() failed");
+        }
+        return fd;
+    }
+
+    StatusOr<int> ppoll(pollfd* fds, nfds_t nfds, double timeout) const override {
+        timespec ts = {};
+        ts.tv_sec = timeout;
+        ts.tv_nsec = (timeout - ts.tv_sec) * 1e9;
+        auto rv = syscallRetry(::ppoll, fds, nfds, &ts, nullptr);
+        if (rv == -1) {
+            return statusFromErrno(errno, "ppoll() failed");
+        }
+        return rv;
+    }
+
+    StatusOr<size_t> writev(Fd fd, const std::vector<iovec>& iov) const override {
+        auto rv = syscallRetry(::writev, fd.get(), iov.data(), iov.size());
+        if (rv == -1) {
+            return statusFromErrno(errno, "writev() failed");
+        }
+        return rv;
+    }
+
+    StatusOr<size_t> write(Fd fd, const Slice buf) const override {
+        auto rv = syscallRetry(::write, fd.get(), buf.base(), buf.size());
+        if (rv == -1) {
+            return statusFromErrno(errno, "write() failed");
+        }
+        return static_cast<size_t>(rv);
+    }
+
+    StatusOr<Slice> read(Fd fd, const Slice buf) const override {
+        auto rv = syscallRetry(::read, fd.get(), buf.base(), buf.size());
+        if (rv == -1) {
+            return statusFromErrno(errno, "read() failed");
+        }
+        return Slice(buf.base(), rv);
+    }
+
+    StatusOr<size_t> sendto(Fd sock, const Slice buf, int flags, const sockaddr* dst,
+                            socklen_t dstlen) const override {
+        auto rv = syscallRetry(::sendto, sock.get(), buf.base(), buf.size(), flags, dst, dstlen);
+        if (rv == -1) {
+            return statusFromErrno(errno, "sendto() failed");
+        }
+        return static_cast<size_t>(rv);
+    }
+
+    StatusOr<Slice> recvfrom(Fd sock, const Slice dst, int flags, sockaddr* src,
+                             socklen_t* srclen) const override {
+        auto rv = syscallRetry(::recvfrom, sock.get(), dst.base(), dst.size(), flags, src, srclen);
+        if (rv == -1) {
+            return statusFromErrno(errno, "recvfrom() failed");
+        }
+        if (rv == 0) {
+            return status::eof;
+        }
+        return take(dst, rv);
+    }
+
+    Status shutdown(Fd fd, int how) const override {
+        auto rv = ::shutdown(fd.get(), how);
+        if (rv == -1) {
+            return statusFromErrno(errno, "shutdown() failed");
+        }
+        return status::ok;
+    }
+
+    Status close(Fd fd) const override {
+        auto rv = ::close(fd.get());
+        if (rv == -1) {
+            return statusFromErrno(errno, "close() failed");
+        }
+        return status::ok;
+    }
+
+    StatusOr<UniqueFile> fopen(const std::string& path, const std::string& mode) const override {
+        UniqueFile file(::fopen(path.c_str(), mode.c_str()));
+        if (file == nullptr) {
+            return statusFromErrno(errno, "fopen(\"" + path + "\", \"" + mode + "\") failed");
+        }
+        return file;
+    }
+
+    StatusOr<pid_t> fork() const override {
+        pid_t rv = ::fork();
+        if (rv == -1) {
+            return statusFromErrno(errno, "fork() failed");
+        }
+        return rv;
+    }
+
+    StatusOr<int> vfprintf(FILE* file, const char* format, va_list ap) const override {
+        auto rv = ::vfprintf(file, format, ap);
+        if (rv == -1) {
+            return statusFromErrno(errno, "vfprintf() failed");
+        }
+        return rv;
+    }
+
+    StatusOr<int> vfscanf(FILE* file, const char* format, va_list ap) const override {
+        auto rv = ::vfscanf(file, format, ap);
+        if (rv == -1) {
+            return statusFromErrno(errno, "vfscanf() failed");
+        }
+        return rv;
+    }
+
+    Status fclose(FILE* file) const override {
+        auto rv = ::fclose(file);
+        if (rv == -1) {
+            return statusFromErrno(errno, "fclose() failed");
+        }
+        return status::ok;
+    }
+};
+
+SyscallsHolder::~SyscallsHolder() {
+    delete &get();
+}
+
+Syscalls& SyscallsHolder::get() {
+    while (true) {
+        // memory_order_relaxed gives the compiler and hardware more
+        // freedom. If we get a stale value (this should only happen
+        // early in the execution of a program) the exchange code below
+        // will loop until we get the most current value.
+        auto* syscalls = mSyscalls.load(std::memory_order_relaxed);
+        // Common case returns existing syscalls
+        if (syscalls) {
+            return *syscalls;
+        }
+
+        // This code will execute on first get()
+        std::unique_ptr<Syscalls> tmp(new RealSyscalls());
+        Syscalls* expected = nullptr;
+        bool success = mSyscalls.compare_exchange_strong(expected, tmp.get());
+        if (success) {
+            // Ownership was transferred to mSyscalls already, must release()
+            return *tmp.release();
+        }
+    }
+}
+
+Syscalls& SyscallsHolder::swap(Syscalls& syscalls) {
+    return *mSyscalls.exchange(&syscalls);
+}
+
+SyscallsHolder sSyscalls;
+
+}  // namespace netdutils
+}  // namespace android