source: vendor/current/source3/lib/msghdr.c

/*
 * Unix SMB/CIFS implementation.
 * Copyright (C) Volker Lendecke 2014
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "replace.h"
#include "lib/msghdr.h"
#include "lib/util/iov_buf.h"
#include <sys/socket.h>

#if defined(HAVE_STRUCT_MSGHDR_MSG_CONTROL)

ssize_t msghdr_prep_fds(struct msghdr *msg, uint8_t *buf, size_t bufsize,
                        const int *fds, size_t num_fds)
{
        size_t fds_size = sizeof(int) * MIN(num_fds, INT8_MAX);
        size_t cmsg_len = CMSG_LEN(fds_size);
        size_t cmsg_space = CMSG_SPACE(fds_size);
        struct cmsghdr *cmsg;
        void *fdptr;

        if (num_fds == 0) {
                if (msg != NULL) {
                        msg->msg_control = NULL;
                        msg->msg_controllen = 0;
                }
                return 0;
        }
        if (num_fds > INT8_MAX) {
                return -1;
        }
        if ((msg == NULL) || (cmsg_space > bufsize)) {
                return cmsg_space;
        }

        msg->msg_control = buf;
        msg->msg_controllen = cmsg_space;

        cmsg = CMSG_FIRSTHDR(msg);
        cmsg->cmsg_level = SOL_SOCKET;
        cmsg->cmsg_type = SCM_RIGHTS;
        cmsg->cmsg_len = cmsg_len;
        fdptr = CMSG_DATA(cmsg);
        memcpy(fdptr, fds, fds_size);
        msg->msg_controllen = cmsg->cmsg_len;

        return cmsg_space;
}

size_t msghdr_prep_recv_fds(struct msghdr *msg, uint8_t *buf, size_t bufsize,
                            size_t num_fds)
{
        size_t ret = CMSG_SPACE(sizeof(int) * num_fds);

        if (bufsize < ret) {
                return ret;
        }
        if (msg != NULL) {
                if (num_fds != 0) {
                        msg->msg_control = buf;
                        msg->msg_controllen = ret;
                } else {
                        msg->msg_control = NULL;
                        msg->msg_controllen = 0;
                }
        }
        return ret;
}

size_t msghdr_extract_fds(struct msghdr *msg, int *fds, size_t fds_size)
{
        struct cmsghdr *cmsg;
        size_t num_fds;

        for(cmsg = CMSG_FIRSTHDR(msg);
            cmsg != NULL;
            cmsg = CMSG_NXTHDR(msg, cmsg))
        {
                if ((cmsg->cmsg_type == SCM_RIGHTS) &&
                    (cmsg->cmsg_level == SOL_SOCKET)) {
                        break;
                }
        }

        if (cmsg == NULL) {
                return 0;
        }

        num_fds = (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int);

        if ((num_fds != 0) && (fds != NULL) && (fds_size >= num_fds)) {
                memcpy(fds, CMSG_DATA(cmsg), num_fds * sizeof(int));
        }

        return num_fds;
}

#elif defined(HAVE_STRUCT_MSGHDR_MSG_ACCRIGHTS)

ssize_t msghdr_prep_fds(struct msghdr *msg, uint8_t *buf, size_t bufsize,
                        const int *fds, size_t num_fds)
{
        size_t needed;

        if (num_fds > INT8_MAX) {
                return -1;
        }

        needed = sizeof(int) * num_fds;

        if ((msg == NULL) || (needed > bufsize)) {
                return needed;
        }

        memcpy(buf, fds, needed);

        msg->msg_accrights = (caddr_t) buf;
        msg->msg_accrightslen = needed;

        return needed;
}

size_t msghdr_prep_recv_fds(struct msghdr *msg, uint8_t *buf, size_t bufsize,
                            size_t num_fds)
{
        size_t ret = num_fds * sizeof(int);

        if (bufsize < ret) {
                return ret;
        }

        if (msg != NULL) {
                if (num_fds != 0) {
                        msg->msg_accrights = (caddr_t) buf;
                        msg->msg_accrightslen = ret;
                } else {
                        msg->msg_accrights = NULL;
                        msg->msg_accrightslen = 0;
                }
        }
        return ret;
}

size_t msghdr_extract_fds(struct msghdr *msg, int *fds, size_t fds_size)
{
        size_t num_fds = msg->msg_accrightslen / sizeof(int);

        if ((fds != 0) && (num_fds <= fds_size)) {
                memcpy(fds, msg->msg_accrights, msg->msg_accrightslen);
        }

        return num_fds;
}

#else

ssize_t msghdr_prep_fds(struct msghdr *msg, uint8_t *buf, size_t bufsize,
                        const int *fds, size_t num_fds)
{
        return -1;
}

size_t msghdr_prep_recv_fds(struct msghdr *msg, uint8_t *buf, size_t bufsize,
                            size_t num_fds)
{
        return 0;
}

size_t msghdr_extract_fds(struct msghdr *msg, int *fds, size_t fds_size)
{
        return 0;
}

#endif

struct msghdr_buf {
        struct msghdr msg;
        struct sockaddr_storage addr;
        struct iovec iov;
        uint8_t buf[];
};

ssize_t msghdr_copy(struct msghdr_buf *msg, size_t msgsize,
                    const void *addr, socklen_t addrlen,
                    const struct iovec *iov, int iovcnt,
                    const int *fds, size_t num_fds)
{
        ssize_t fd_len;
        size_t iov_len, needed, bufsize;

        bufsize = (msgsize > offsetof(struct msghdr_buf, buf)) ?
                msgsize - offsetof(struct msghdr_buf, buf) : 0;

        if (msg != NULL) {
                msg->msg = (struct msghdr) { 0 };

                fd_len = msghdr_prep_fds(&msg->msg, msg->buf, bufsize,
                                         fds, num_fds);
        } else {
                fd_len = msghdr_prep_fds(NULL, NULL, bufsize, fds, num_fds);
        }

        if (fd_len == -1) {
                return -1;
        }

        if (bufsize >= fd_len) {
                bufsize -= fd_len;
        } else {
                bufsize = 0;
        }

        if (msg != NULL) {

                if (addr != NULL) {
                        if (addrlen > sizeof(struct sockaddr_storage)) {
                                errno = EMSGSIZE;
                                return -1;
                        }
                        memcpy(&msg->addr, addr, addrlen);
                        msg->msg.msg_name = &msg->addr;
                        msg->msg.msg_namelen = addrlen;
                } else {
                        msg->msg.msg_name = NULL;
                        msg->msg.msg_namelen = 0;
                }

                msg->iov.iov_base = msg->buf + fd_len;
                msg->iov.iov_len = iov_buf(
                        iov, iovcnt, msg->iov.iov_base, bufsize);
                iov_len = msg->iov.iov_len;

                msg->msg.msg_iov = &msg->iov;
                msg->msg.msg_iovlen = 1;
        } else {
                iov_len = iov_buflen(iov, iovcnt);
        }

        needed = offsetof(struct msghdr_buf, buf) + fd_len;
        if (needed < fd_len) {
                return -1;
        }
        needed += iov_len;
        if (needed < iov_len) {
                return -1;
        }

        return needed;
}

struct msghdr *msghdr_buf_msghdr(struct msghdr_buf *msg)
{
        return &msg->msg;
}