fuzz: Add fuzzer for virtio-net

To synthesize the interactions between the virtio-net device and the tap
interface, the fuzzer utilizes a pair of unix domain sockets: one socket
(e.g. the dummy tap frontend) is used to construct the 'net_util::Tap'
instance for creating a virtio-net device; the other socket (e.g. the
dummy tap backend) is used in a epoll loop for handling the tx and rx
requests from the virtio-net device.

Signed-off-by: Bo Chen <chen.bo@intel.com>

fuzz/Cargo.toml

@@ -15,6 +15,7 @@ epoll = "4.3.1"
 libc = "0.2.135"
 libfuzzer-sys = "0.4.5"
 micro_http = { git = "https://github.com/firecracker-microvm/micro-http", branch = "main" }
+net_util = { path = "../net_util" }
 once_cell = "1.16.0"
 qcow = { path = "../qcow" }
 seccompiler = "0.3.0"
@@ -80,6 +81,12 @@ path = "fuzz_targets/mem.rs"
 test = false
 doc = false
 
+[[bin]]
+name = "net"
+path = "fuzz_targets/net.rs"
+test = false
+doc = false
+
 [[bin]]
 name = "pmem"
 path = "fuzz_targets/pmem.rs"