plugin: Add support for tap fd on the command line

Add support for having the tap fd be passed in on the command line the
same way we do for linux.

BUG=b:80150167
TEST=run plugin_net_config (after changing the expected ip/netmask/mac
     address appropriately)

Change-Id: Ic81b167b7bb2caa71ce5931921b87d9eeca69af9
Signed-off-by: Chirantan Ekbote <chirantan@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1341105

1 files changed, 17 insertions, 3 deletions

diff --git a/src/plugin/mod.rs b/src/plugin/mod.rs
index c833197..4f50d5e 100644
--- a/src/plugin/mod.rs
+++ b/src/plugin/mod.rs
@@ -28,9 +28,9 @@ use io_jail::{self, Minijail};
 use kvm::{Datamatch, IoeventAddress, Kvm, Vcpu, VcpuExit, Vm};
 use net_util::{Error as TapError, Tap, TapT};
 use sys_util::{
-    block_signal, clear_signal, getegid, geteuid, register_signal_handler, Error as SysError,
-    EventFd, GuestMemory, Killable, MmapError, PollContext, PollToken, Result as SysResult,
-    SignalFd, SignalFdError, SIGRTMIN,
+    block_signal, clear_signal, getegid, geteuid, register_signal_handler, validate_raw_fd,
+    Error as SysError, EventFd, GuestMemory, Killable, MmapError, PollContext, PollToken,
+    Result as SysResult, SignalFd, SignalFdError, SIGRTMIN,
 };
 
 use Config;
@@ -54,6 +54,7 @@ pub enum Error {
     CreatePollContext(SysError),
     CreateSignalFd(SignalFdError),
     CreateSocketPair(io::Error),
+    CreateTapFd(TapError),
     CreateVcpu(SysError),
     CreateVcpuSocket(SysError),
     CreateVm(SysError),
@@ -97,6 +98,7 @@ pub enum Error {
     TapSetNetmask(TapError),
     TapSetMacAddress(TapError),
     TapEnable(TapError),
+    ValidateTapFd(SysError),
 }
 
 impl fmt::Display for Error {
@@ -115,6 +117,9 @@ impl fmt::Display for Error {
             Error::CreatePollContext(ref e) => write!(f, "failed to create poll context: {:?}", e),
             Error::CreateSignalFd(ref e) => write!(f, "failed to create signalfd: {:?}", e),
             Error::CreateSocketPair(ref e) => write!(f, "failed to create socket pair: {}", e),
+            Error::CreateTapFd(ref e) => {
+                write!(f, "failed to create tap device from raw fd: {:?}", e)
+            }
             Error::CreateVcpu(ref e) => write!(f, "error creating vcpu: {:?}", e),
             Error::CreateVcpuSocket(ref e) => {
                 write!(f, "error creating vcpu request socket: {:?}", e)
@@ -172,6 +177,7 @@ impl fmt::Display for Error {
             Error::TapSetNetmask(ref e) => write!(f, "error setting tap netmask: {:?}", e),
             Error::TapSetMacAddress(ref e) => write!(f, "error setting tap mac address: {:?}", e),
             Error::TapEnable(ref e) => write!(f, "error enabling tap device: {:?}", e),
+            Error::ValidateTapFd(ref e) => write!(f, "failed to validate raw tap fd: {:?}", e),
         }
     }
 }
@@ -507,6 +513,14 @@ pub fn run_config(cfg: Config) -> Result<()> {
             }
         }
     }
+    if let Some(tap_fd) = cfg.tap_fd {
+        // Safe because we ensure that we get a unique handle to the fd.
+        let tap = unsafe {
+            Tap::from_raw_fd(validate_raw_fd(tap_fd).map_err(Error::ValidateTapFd)?)
+                .map_err(Error::CreateTapFd)?
+        };
+        tap_opt = Some(tap);
+    }
 
     let plugin_args: Vec<&str> = cfg.params.iter().map(|s| &s[..]).collect();