vtysh: receive file descriptors from daemons

The other half of yielding back a file descriptor from a daemon to
vtysh.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>

diff --git a/vtysh/vtysh.c b/vtysh/vtysh.c
index fe7a2e73ffce520aae83b195e5ff67402af3f485..2b9b2b4cca2a28a88ec87c4be1cc6c18346a84ca 100644 (file)
--- a/vtysh/vtysh.c
+++ b/vtysh/vtysh.c
@@ -182,6 +182,53 @@ static void vclient_close(struct vtysh_client *vclient)
        }
 }
 
+static ssize_t vtysh_client_receive(struct vtysh_client *vclient,
+                                   char *buf, size_t bufsz, int *pass_fd)
+{
+       struct iovec iov[1] = {
+               {
+                       .iov_base = buf,
+                       .iov_len = bufsz,
+               },
+       };
+       union {
+               uint8_t buf[CMSG_SPACE(sizeof(int))];
+               struct cmsghdr align;
+       } u;
+       struct msghdr mh = {
+               .msg_iov = iov,
+               .msg_iovlen = array_size(iov),
+               .msg_control = u.buf,
+               .msg_controllen = sizeof(u.buf),
+       };
+       struct cmsghdr *cmh = CMSG_FIRSTHDR(&mh);
+       ssize_t ret;
+
+       cmh->cmsg_level = SOL_SOCKET;
+       cmh->cmsg_type = SCM_RIGHTS;
+       cmh->cmsg_len = CMSG_LEN(sizeof(int));
+       memset(CMSG_DATA(cmh), -1, sizeof(int));
+
+       do {
+               ret = recvmsg(vclient->fd, &mh, 0);
+               if (ret < 0 && (errno == EINTR || errno == EAGAIN))
+                       continue;
+       } while (false);
+
+       if (cmh->cmsg_len == CMSG_LEN(sizeof(int))) {
+               int fd;
+
+               memcpy(&fd, CMSG_DATA(cmh), sizeof(int));
+               if (fd != -1) {
+                       if (pass_fd)
+                               *pass_fd = fd;
+                       else
+                               close(fd);
+               }
+       }
+       return ret;
+}
+
 /*
  * Send a CLI command to a client and read the response.
  *
@@ -205,7 +252,8 @@ static void vclient_close(struct vtysh_client *vclient)
  *    a status code
  */
 static int vtysh_client_run(struct vtysh_client *vclient, const char *line,
-                           void (*callback)(void *, const char *), void *cbarg)
+                           void (*callback)(void *, const char *), void *cbarg,
+                           int *pass_fd)
 {
        int ret;
        char stackbuf[4096];
@@ -239,8 +287,11 @@ static int vtysh_client_run(struct vtysh_client *vclient, const char *line,
 
        bufvalid = buf;
        do {
-               ssize_t nread =
-                       read(vclient->fd, bufvalid, buf + bufsz - bufvalid - 1);
+               ssize_t nread;
+
+               nread = vtysh_client_receive(vclient, bufvalid,
+                                            buf + bufsz - bufvalid - 1,
+                                            pass_fd);
 
                if (nread < 0 && (errno == EINTR || errno == EAGAIN))
                        continue;
@@ -382,7 +433,7 @@ static int vtysh_client_run_all(struct vtysh_client *head_client,
        int correct_instance = 0, wrong_instance = 0;
 
        for (client = head_client; client; client = client->next) {
-               rc = vtysh_client_run(client, line, callback, cbarg);
+               rc = vtysh_client_run(client, line, callback, cbarg, NULL);
                if (rc == CMD_NOT_MY_INSTANCE) {
                        wrong_instance++;
                        continue;