build: Bump getrandom from 0.2.15 to 0.3.1

Manually bump `getrandom` due to API changes.

Bumps [getrandom](https://github.com/rust-random/getrandom) from 0.2.15 to 0.3.1.
- [Changelog](https://github.com/rust-random/getrandom/blob/master/CHANGELOG.md)
- [Commits](rust-random/getrandom@v0.2.15...v0.3.1)

Signed-off-by: Ruoqing He <heruoqing@iscas.ac.cn>

net_util/Cargo.toml

@@ -6,7 +6,7 @@ version = "0.1.0"
 
 [dependencies]
 epoll = "4.3.3"
-getrandom = "0.2.15"
+getrandom = "0.3.1"
 libc = "0.2.167"
 log = "0.4.22"
 net_gen = { path = "../net_gen" }

net_util/src/mac.rs

@@ -80,7 +80,7 @@ impl MacAddr {
     pub fn local_random() -> MacAddr {
         // Generate a fully random MAC
         let mut random_bytes = [0u8; MAC_ADDR_LEN];
-        if let Err(e) = getrandom::getrandom(&mut random_bytes) {
+        if let Err(e) = getrandom::fill(&mut random_bytes) {
             error!(
                 "Error populating MAC address with random data: {}",
                 e.to_string()