96 lines
2.7 KiB
C++
96 lines
2.7 KiB
C++
#include "c-calls.hh"
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#include "lix/libutil/file-system.hh"
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#include "lix/libutil/processes.hh"
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#include "lix/libutil/unix-domain-socket.hh"
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#include "lix/libutil/strings.hh"
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#include <string>
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#include <sys/socket.h>
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#include <sys/un.h>
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#include <unistd.h>
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namespace nix {
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AutoCloseFD createUnixDomainSocket()
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{
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AutoCloseFD fdSocket{socket(PF_UNIX, SOCK_STREAM
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#ifdef SOCK_CLOEXEC
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| SOCK_CLOEXEC
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#endif
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, 0)};
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if (!fdSocket)
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throw SysError("cannot create Unix domain socket");
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closeOnExec(fdSocket.get());
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return fdSocket;
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}
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AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode)
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{
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auto fdSocket = nix::createUnixDomainSocket();
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bind(fdSocket.get(), path);
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chmodPath(path, mode);
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if (listen(fdSocket.get(), 100) == -1)
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throw SysError("cannot listen on socket '%1%'", path);
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return fdSocket;
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}
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/**
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* Workaround for the max length of Unix socket names being between 102
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* (darwin) and 108 (Linux), which is extremely short. This limitation is
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* caused by historical restrictions on sizeof(struct sockaddr):
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* https://unix.stackexchange.com/a/367012.
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*
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* Our solution here is to start a process inheriting the socket, chdir into
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* the directory of the socket, then connect with just the filename. This is
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* rather silly but it works around working directory being process-wide state,
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* and is as clearly sound as possible.
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*/
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static void bindConnectProcHelper(
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std::string_view operationName, auto && operation,
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int fd, const std::string & path)
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{
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struct sockaddr_un addr;
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addr.sun_family = AF_UNIX;
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// Casting between types like these legacy C library interfaces
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// require is forbidden in C++. To maintain backwards
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// compatibility, the implementation of the bind/connect functions
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// contains some hints to the compiler that allow for this
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// special case.
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auto * psaddr = reinterpret_cast<struct sockaddr *>(&addr);
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if (path.size() + 1 >= sizeof(addr.sun_path)) {
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runHelper(
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"unix-bind-connect",
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{.args =
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{std::to_string(fd), std::string(operationName), dirOf(path), std::string(baseNameOf(path))},
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.redirections = {{.dup = fd, .from = fd}}}
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).waitAndCheck();
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} else {
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memcpy(addr.sun_path, path.c_str(), path.size() + 1);
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if (operation(fd, psaddr, sizeof(addr)) == -1)
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throw SysError("cannot %s to socket at '%s'", operationName, path);
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}
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}
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void bind(int fd, const std::string & path)
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{
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(void) sys::unlink(path);
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bindConnectProcHelper("bind", ::bind, fd, path);
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}
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void connect(int fd, const std::string & path)
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{
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bindConnectProcHelper("connect", ::connect, fd, path);
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}
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}
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