Add support for multiple network interfaces

Allow --tap-fd to be given mutliple times, a different virtual network
card will be added each time the flag is given.
Additionally, --tap-fd is no longer mutually exclusive with --host-ip,
etc.

Bug=chromium:931470
Test=booted cuttlefish device with multiple network cards

Change-Id: I4108f97c7f4b19db12fcb3c533088a04a58e56db
Reviewed-on: https://chromium-review.googlesource.com/1469222
Commit-Ready: Jorge Moreira Broche <jemoreira@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Tested-by: Jorge Moreira Broche <jemoreira@google.com>
Reviewed-by: Dylan Reid <dgreid@chromium.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/linux.rs b/src/linux.rs
index b81bc71..1dbd8fd 100644
--- a/src/linux.rs
+++ b/src/linux.rs
@@ -432,7 +432,7 @@ fn create_virtio_devs(
     });
 
     // We checked above that if the IP is defined, then the netmask is, too.
-    if let Some(tap_fd) = cfg.tap_fd {
+    for tap_fd in 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::ValidateRawFd)?)
@@ -449,7 +449,9 @@ fn create_virtio_devs(
         };
 
         devs.push(VirtioDeviceStub { dev: net_box, jail });
-    } else if let Some(host_ip) = cfg.host_ip {
+    }
+
+    if let Some(host_ip) = cfg.host_ip {
         if let Some(netmask) = cfg.netmask {
             if let Some(mac_address) = cfg.mac_address {
                 let net_box: Box<devices::virtio::VirtioDevice> = if cfg.vhost_net {