From 759ef658680949d37f3bb3589804e85fae0596f7 Mon Sep 17 00:00:00 2001 Message-Id: <759ef658680949d37f3bb3589804e85fae0596f7.1715554061.git.mdw@distorted.org.uk> From: Mark Wooding Date: Sat, 29 Nov 2003 11:58:49 +0000 Subject: [PATCH] File descriptor passing. Organization: Straylight/Edgeware From: mdw --- fdpass.c | 162 +++++++++++++++++++++++++++++++++++++++++++++++++++ fdpass.h | 92 +++++++++++++++++++++++++++++ man/fdpass.3 | 54 +++++++++++++++++ 3 files changed, 308 insertions(+) create mode 100644 fdpass.c create mode 100644 fdpass.h create mode 100644 man/fdpass.3 diff --git a/fdpass.c b/fdpass.c new file mode 100644 index 0000000..95685e7 --- /dev/null +++ b/fdpass.c @@ -0,0 +1,162 @@ +/* -*-c-*- + * + * $Id: fdpass.c,v 1.1 2003/11/29 11:58:49 mdw Exp $ + * + * File descriptor passing + * + * (c) 2003 Straylight/Edgeware + */ + +/*----- Licensing notice --------------------------------------------------* + * + * This file is part of the mLib utilities library. + * + * mLib is free software; you can redistribute it and/or modify + * it under the terms of the GNU Library General Public License as + * published by the Free Software Foundation; either version 2 of the + * License, or (at your option) any later version. + * + * mLib is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU Library General Public License for more details. + * + * You should have received a copy of the GNU Library General Public + * License along with mLib; if not, write to the Free + * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, + * MA 02111-1307, USA. + */ + +/*----- Revision history --------------------------------------------------* + * + * $Log: fdpass.c,v $ + * Revision 1.1 2003/11/29 11:58:49 mdw + * File descriptor passing. + * + */ + +/*----- Header files ------------------------------------------------------*/ + +#include +#include +#include +#include + +#include +#include +#include +#include +#include +#include + +#include "fdpass.h" + +/*----- Main code ---------------------------------------------------------*/ + +/* --- @fdpass_send@ --- * + * + * Arguments: @int sock@ = socket to send over + * @int fd@ = file descriptor to send + * @const void *p@ = pointer to data to send + * @size_t sz@ = size of buffer to send + * + * Returns: On error, @-1@, otherwise number of bytes transferred from + * @p@. + * + * Use: Sends a copy of file descriptor @fd@ to the other end of + * @sock@. + */ + +ssize_t fdpass_send(int sock, int fd, const void *p, size_t sz) +{ + struct iovec iov; + struct msghdr msg; +#ifndef HAVE_MSG_ACCRIGHTS + char buf[CMSG_SPACE(sizeof(fd))]; + struct cmsghdr *cmsg; +#endif + + iov.iov_base = (/*unconst*/ void *)p; + iov.iov_len = sz; + msg.msg_name = 0; + msg.msg_namelen = 0; + msg.msg_iov = &iov; + msg.msg_iovlen = 1; + msg.msg_flags = 0; +#ifdef HAVE_MSG_ACCRIGHTS + msg.msg_accrights = &fd; + msg.msg_accrightslen = sizeof(fd); +#else + msg.msg_control = buf; + msg.msg_controllen = sizeof(buf); + cmsg = CMSG_FIRSTHDR(&msg); + cmsg->cmsg_len = CMSG_LEN(sizeof(fd)); + cmsg->cmsg_level = SOL_SOCKET; + cmsg->cmsg_type = SCM_RIGHTS; + memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd)); +#endif + return (sendmsg(sock, &msg, 0)); +} + +/* --- @fdpass_recv@ --- * + * + * Arguments: @int sock@ = socket to send over + * @int *fd@ = where to put received descriptor + * @void *p@ = pointer to where to put data + * @size_t sz@ = size of buffer + * + * Returns: On error, @-1@, otherwise number of bytes transferred. + * + * Use: Receives a file descriptor. If the call succeeds, and there + * was a file descriptor, then @fd@ won't be @-1@ on exit; + * otherwise it will. At most one descriptor will be collected. + */ + +ssize_t fdpass_recv(int sock, int *fd, void *p, size_t sz) +{ + struct iovec iov; + struct msghdr msg; + ssize_t rc; +#ifndef HAVE_MSG_ACCRIGHTS + char buf[CMSG_SPACE(sizeof(fd))]; + struct cmsghdr *cmsg; + int fdtmp; +#endif + + *fd = -1; + iov.iov_base = p; + iov.iov_len = sz; + msg.msg_name = 0; + msg.msg_namelen = 0; + msg.msg_iov = &iov; + msg.msg_iovlen = 1; + msg.msg_flags = 0; +#ifdef HAVE_MSG_ACCRIGHTS + msg.msg_accrights = fd; + msg.msg_accrightslen = sizeof(*fd); +#else + msg.msg_control = buf; + msg.msg_controllen = sizeof(buf); +#endif + if ((rc = recvmsg(sock, &msg, 0)) < 0) + return (rc); +#ifdef HAVE_MSG_ACCRIGHTS + if (msg.msg_accrightslen < sizeof(*fd)) + *fd = -1; +#else + for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) { + if (cmsg->cmsg_level == SOL_SOCKET && + cmsg->cmsg_type == SCM_RIGHTS && + cmsg->cmsg_len >= CMSG_LEN(sizeof(fd))) { + memcpy(&fdtmp, CMSG_DATA(cmsg), sizeof(fdtmp)); + if (*fd == -1) + *fd = fdtmp; + else + close(fdtmp); + } + } +#endif + return (rc); +} + +/*----- That's all, folks -------------------------------------------------*/ diff --git a/fdpass.h b/fdpass.h new file mode 100644 index 0000000..0e14078 --- /dev/null +++ b/fdpass.h @@ -0,0 +1,92 @@ +/* -*-c-*- + * + * $Id: fdpass.h,v 1.1 2003/11/29 11:58:49 mdw Exp $ + * + * File descriptor passing + * + * (c) 2003 Straylight/Edgeware + */ + +/*----- Licensing notice --------------------------------------------------* + * + * This file is part of the mLib utilities library. + * + * mLib is free software; you can redistribute it and/or modify + * it under the terms of the GNU Library General Public License as + * published by the Free Software Foundation; either version 2 of the + * License, or (at your option) any later version. + * + * mLib is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU Library General Public License for more details. + * + * You should have received a copy of the GNU Library General Public + * License along with mLib; if not, write to the Free + * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, + * MA 02111-1307, USA. + */ + +/*----- Revision history --------------------------------------------------* + * + * $Log: fdpass.h,v $ + * Revision 1.1 2003/11/29 11:58:49 mdw + * File descriptor passing. + * + */ + +#ifndef MLIB_FDPASS_H +#define MLIB_FDPASS_H + +#ifdef __cplusplus + extern "C" { +#endif + +/*----- Header files ------------------------------------------------------*/ + +#include +#include + +/*----- Functions provided ------------------------------------------------*/ + +/* --- @fdpass_send@ --- * + * + * Arguments: @int sock@ = socket to send over + * @int fd@ = file descriptor to send + * @const void *p@ = pointer to data to send + * @size_t sz@ = size of buffer to send + * + * Returns: On error, @-1@, otherwise number of bytes transferred from + * @p@. + * + * Use: Sends a copy of file descriptor @fd@ to the other end of + * @sock@. + */ + +extern ssize_t fdpass_send(int /*sock*/, int /*fd*/, + const void */*p*/, size_t /*sz*/); + +/* --- @fdpass_recv@ --- * + * + * Arguments: @int sock@ = socket to send over + * @int *fd@ = where to put received descriptor + * @void *p@ = pointer to where to put data + * @size_t sz@ = size of buffer + * + * Returns: On error, @-1@, otherwise number of bytes transferred. + * + * Use: Receives a file descriptor. If the call succeeds, and there + * was a file descriptor, then @fd@ won't be @-1@ on exit; + * otherwise it will. At most one descriptor will be collected. + */ + +extern ssize_t fdpass_recv(int /*sock*/, int */*fd*/, + void */*p*/, size_t /*sz*/); + +/*----- That's all, folks -------------------------------------------------*/ + +#ifdef __cplusplus + } +#endif + +#endif diff --git a/man/fdpass.3 b/man/fdpass.3 new file mode 100644 index 0000000..6a91ec1 --- /dev/null +++ b/man/fdpass.3 @@ -0,0 +1,54 @@ +.\" -*-nroff-*- +.TH fdpass 3 "28 November 2003" "Straylight/Edgeware" "mLib utilities library" +.SH NAME +fdpass \- file descriptor passing +.\" @fdpass_send +.\" @fdpass_recv +.SH SYNOPSIS +.nf +.B "#include " + +.BI "ssize_t fdpass_send(int " sock ", int " fd ", const void *" p ", size_t " sz ); +.BI "ssize_t fdpass_recv(int " sock ", int *" fd ", void *" p ", size_t " sz ); +.fi +.SH DESCRIPTION +The function +.B fdpass_send +sends the file descriptor +.I fd +as ancillary data attached to the buffer pointed to by +.I p +of length +.I sz +over the Unix-domain socket +.IR sock . +It returns the amount of data sent, or \-1 on error. For more details, +see +.BR sendmsg (2) +and +.BR unix (7). +.PP +The function +.B fdpass_recv +receives at most +.I sz +bytes of data into the buffer pointed to by +.IR p , +together with at most one file descriptor passed as ancillary data, +which is written to the integer pointed to by +.IR fd . +Other file descriptors received are closed; any other ancillary messages +are ignored. If no file descriptor is received, +.BI * fd +is set to \-1. The function returns the number of bytes read, or \-1 on +error. For more details, see +.BR recvmsg (2) +and +.BR unix (7). +.SH "SEE ALSO" +.BR recvmsg (2), +.BR sendmsg (2), +.BR mLib (3), +.BR unix (7). +.SH AUTHOR +Mark Wooding, -- [mdw]