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Re: [libvirt] [PATCH v2 5/8] LXC: Creating devices for container on host side



----- Urspr√ľngliche Mail -----
> user namespace doesn't allow to create devices in
> uninit userns. We should create devices on host side.
> 
> Signed-off-by: Gao feng <gaofeng cn fujitsu com>
> ---
>  src/lxc/lxc_container.c  | 47 +++++++----------------------
>  src/lxc/lxc_controller.c | 77
>  ++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 87 insertions(+), 37 deletions(-)
> 
> diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
> index eabaa34..540246f 100644
> --- a/src/lxc/lxc_container.c
> +++ b/src/lxc/lxc_container.c
> @@ -833,22 +833,10 @@ cleanup:
>      return ret;
>  }
>  
> -static int lxcContainerPopulateDevices(char **ttyPaths, size_t
> nttyPaths)
> +static int lxcContainerSetupDevices(char **ttyPaths, size_t
> nttyPaths)
>  {
>      size_t i;
>      const struct {
> -        int maj;
> -        int min;
> -        mode_t mode;
> -        const char *path;
> -    } devs[] = {
> -        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_NULL, 0666, "/dev/null" },
> -        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_ZERO, 0666, "/dev/zero" },
> -        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_FULL, 0666, "/dev/full" },
> -        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_RANDOM, 0666,
> "/dev/random" },
> -        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_URANDOM, 0666,
> "/dev/urandom" },
> -    };
> -    const struct {
>          const char *src;
>          const char *dst;
>      } links[] = {
> @@ -858,18 +846,6 @@ static int lxcContainerPopulateDevices(char
> **ttyPaths, size_t nttyPaths)
>          { "/proc/self/fd", "/dev/fd" },
>      };
>  
> -    /* Populate /dev/ with a few important bits */
> -    for (i = 0 ; i < ARRAY_CARDINALITY(devs) ; i++) {
> -        dev_t dev = makedev(devs[i].maj, devs[i].min);
> -        if (mknod(devs[i].path, S_IFCHR, dev) < 0 ||
> -            chmod(devs[i].path, devs[i].mode)) {
> -            virReportSystemError(errno,
> -                                 _("Failed to make device %s"),
> -                                 devs[i].path);
> -            return -1;
> -        }
> -    }
> -
>      for (i = 0 ; i < ARRAY_CARDINALITY(links) ; i++) {
>          if (symlink(links[i].src, links[i].dst) < 0) {
>              virReportSystemError(errno,
> @@ -882,22 +858,13 @@ static int lxcContainerPopulateDevices(char
> **ttyPaths, size_t nttyPaths)
>      if (access("/dev/pts/ptmx", W_OK) == 0) {
>          /* We have private devpts capability, so bind that */
>          if (virFileTouch("/dev/ptmx", 0666) < 0)
> -            return -1;
> +           return -1;
>  
>          if (mount("/dev/pts/ptmx", "/dev/ptmx", "ptmx", MS_BIND,
>          NULL) < 0) {
>              virReportSystemError(errno, "%s",
>                                   _("Failed to bind /dev/pts/ptmx on
>                                   to /dev/ptmx"));
>              return -1;
>          }
> -    } else {
> -        /* Legacy devpts, so we need to just use shared one */
> -        dev_t dev = makedev(LXC_DEV_MAJ_TTY, LXC_DEV_MIN_PTMX);
> -        if (mknod("/dev/ptmx", S_IFCHR, dev) < 0 ||
> -            chmod("/dev/ptmx", 0666)) {
> -            virReportSystemError(errno, "%s",
> -                                 _("Failed to make device
> /dev/ptmx"));
> -            return -1;
> -        }
>      }
>  
>      for (i = 0 ; i < nttyPaths ; i++) {
> @@ -1825,8 +1792,8 @@ static int
> lxcContainerSetupPivotRoot(virDomainDefPtr vmDef,
>      if (lxcContainerMountFSDevPTS(vmDef, "/.oldroot") < 0)
>          goto cleanup;
>  
> -    /* Populates device nodes in /dev/ */
> -    if (lxcContainerPopulateDevices(ttyPaths, nttyPaths) < 0)
> +    /* Sets up device nodes in /dev/ */
> +    if (lxcContainerSetupDevices(ttyPaths, nttyPaths) < 0)
>          goto cleanup;
>  
>      /* Sets up any non-root mounts from guest config */
> @@ -2037,6 +2004,12 @@ static int lxcContainerChild(void *data)
>          goto cleanup;
>      }
>  
> +    if (lxcContainerWaitForContinue(argv->monitor) < 0) {
> +        virReportSystemError(errno, "%s",
> +                             _("Failed to read the container
> continue message"));
> +        goto cleanup;
> +    }
> +
>      ret = 0;
>  cleanup:
>      VIR_FREE(ttyPath);
> diff --git a/src/lxc/lxc_controller.c b/src/lxc/lxc_controller.c
> index e9b90bf..2072e9a 100644
> --- a/src/lxc/lxc_controller.c
> +++ b/src/lxc/lxc_controller.c
> @@ -1103,6 +1103,73 @@ cleanup:
>  }
>  
>  
> +static int virLXCControllerPopulateDevices(virLXCControllerPtr ctrl)
> +{
> +    size_t i;
> +    int ret = -1;
> +    char *ptmx = NULL;
> +    char *path = NULL;
> +    const struct {
> +        int maj;
> +        int min;
> +        mode_t mode;
> +        const char *path;
> +    } devs[] = {
> +        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_NULL, 0666, "/dev/null" },
> +        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_ZERO, 0666, "/dev/zero" },
> +        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_FULL, 0666, "/dev/full" },
> +        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_RANDOM, 0666,
> "/dev/random" },
> +        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_URANDOM, 0666,
> "/dev/urandom" },
> +    };
> +
> +    /* Populate /dev/ with a few important bits */
> +    for (i = 0 ; i < ARRAY_CARDINALITY(devs) ; i++) {
> +        if (virAsprintf(&path, "/proc/%llu/root/%s",
> +                        (unsigned long long)ctrl->initpid,
> +                        devs[i].path) < 0) {
> +            virReportOOMError();
> +            goto out;
> +        }
> +
> +        dev_t dev = makedev(devs[i].maj, devs[i].min);
> +        if (mknod(path, S_IFCHR, dev) < 0 ||
> +            chmod(path, devs[i].mode)) {
> +            virReportSystemError(errno,
> +                                 _("Failed to make device %s"),
> +                                 devs[i].path);
> +            goto out;
> +        }
> +    }
> +
> +    if (virAsprintf(&ptmx, "/proc/%llu/root/dev/pts/ptmx",
> +                    (unsigned long long)ctrl->initpid) < 0) {
> +        virReportOOMError();
> +        goto out;
> +    }
> +
> +    if (access(ptmx, W_OK)) {
> +        VIR_FREE(path);
> +
> +        if (virAsprintf(&path, "/proc/%llu/root/dev/ptmx",
> +                        (unsigned long long)ctrl->initpid) < 0) {
> +            virReportOOMError();
> +            goto out;
> +        }
> +        /* Legacy devpts, so we need to just use shared one */
> +        dev_t dev = makedev(LXC_DEV_MAJ_TTY, LXC_DEV_MIN_PTMX);
> +        if (mknod(path, S_IFCHR, dev) < 0 ||
> +            chmod(path, 0666)) {
> +            virReportSystemError(errno,  _("Failed to make device
> %s"), path);
> +            goto out;
> +        }
> +    }
> +
> +    ret = 0;
> +out:
> +    VIR_FREE(ptmx);
> +    VIR_FREE(path);
> +    return ret;
> +}
>  
>  /**
>   * virLXCControllerMoveInterfaces
> @@ -1552,6 +1619,16 @@ virLXCControllerRun(virLXCControllerPtr ctrl)
>          goto cleanup;
>      }
>  
> +    /* Populate devices for container */
> +    if (virLXCControllerPopulateDevices(ctrl) < 0)
> +        goto cleanup;

systemd will be not happy with this.
If /dev/ is not already a mountpoint it will try to mount devtmpfs which
will fail an systemd stops booting.

It would be nice to have:
a) A way to disable virLXCControllerPopulateDevices(), i.e. one bind mounts his own lxc-/dev to /dev
b) libvirt mounts a tmpfs onto /dev and then creates the devices nodes.

Thanks,
//richard


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