87 lines
2.7 KiB
C++
87 lines
2.7 KiB
C++
 
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#include "network.hpp"
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#include <fcntl.h>
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#include <poll.h>
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#include <sys/prctl.h>
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#include <signal.h>
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#include <sys/wait.h>
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#include <unistd.h>
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#include <cstring>
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#include <fstream>
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#include <stdexcept>
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#include "spec.hpp"
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#include "util.hpp"
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namespace doos {
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NetMode Network::parse(const std::string& s) {
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if (s == "slirp") return NetMode::Slirp;
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if (s == "host") return NetMode::Host;
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if (s == "none") return NetMode::None;
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throw std::runtime_error("unknown network mode '" + s + "' (use slirp, host or none)");
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}
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std::string Network::name(NetMode m) {
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switch (m) {
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case NetMode::Slirp: return "slirp";
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case NetMode::Host: return "host";
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case NetMode::None: return "none";
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}
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return "?";
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}
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std::string Network::resolvConf(NetMode m) {
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switch (m) {
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case NetMode::Slirp: return "nameserver " + std::string(spec::kSlirpDns) + "\n";
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case NetMode::None: return "";
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case NetMode::Host: {
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// Host netns is shared, so the host resolver config is valid. Stub on 127.0.0.53 works too.
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std::ifstream in("/etc/resolv.conf");
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return std::string(std::istreambuf_iterator<char>(in), {});
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}
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}
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return "";
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}
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void SlirpSession::start(pid_t targetPid) {
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int ready[2];
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if (::pipe2(ready, O_CLOEXEC) != 0) throw SysError("pipe");
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Fd readEnd(ready[0]), writeEnd(ready[1]);
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pid_ = ::fork();
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if (pid_ < 0) throw SysError("fork slirp4netns");
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if (pid_ == 0) {
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::prctl(PR_SET_PDEATHSIG, SIGKILL);
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int nul = ::open("/dev/null", O_WRONLY);
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if (nul >= 0) { ::dup2(nul, 1); ::dup2(nul, 2); }
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int wfd = ::dup(writeEnd.get()); // dup clears CLOEXEC
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std::string readyArg = "--ready-fd=" + std::to_string(wfd);
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std::string target = std::to_string(targetPid);
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std::string bin(spec::kSlirpBinary), tap(spec::kSlirpTapName);
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::execlp(bin.c_str(), bin.c_str(), "--configure", "--mtu=65520", "--disable-host-loopback",
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readyArg.c_str(), target.c_str(), tap.c_str(), static_cast<char*>(nullptr));
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::dprintf(2, "doos: cannot exec %s: %s\n", bin.c_str(), std::strerror(errno));
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::_exit(127);
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}
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writeEnd.reset();
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pollfd p{readEnd.get(), POLLIN, 0};
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int rc = ::poll(&p, 1, spec::kNetReadyTimeoutMs);
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char c = 0;
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if (rc > 0 && ::read(readEnd.get(), &c, 1) == 1) return;
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stop();
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throw std::runtime_error(rc == 0 ? "slirp4netns not ready in time"
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: "slirp4netns failed to start (is it installed and permitted?)");
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}
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void SlirpSession::stop() {
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if (pid_ <= 0) return;
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::kill(pid_, SIGTERM);
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::waitpid(pid_, nullptr, 0);
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pid_ = -1;
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}
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} // namespace doos
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