增加对dhcpv4的支持（tcp、udp socket已写好，但由于缺少epoll机制，尚未完整测试） (#237)

* 为virtio网卡完成smoltcp的phy层配置

* raw socket

* 初步写完udp和tcp socket

* 能够正常通过dhcp获取ipv4地址（具有全局iface btree)

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Co-authored-by: guanjinquan <1666320330@qq.com>

kernel/src/arch/x86_64/mod.rs

@@ -6,4 +6,5 @@ pub mod fpu;
 pub mod interrupt;
 pub mod mm;
 pub mod pci;
+pub mod rand;
 pub mod sched;

kernel/src/arch/x86_64/rand.rs

@@ -0,0 +1,5 @@
+use core::arch::x86_64::_rdtsc;
+
+pub fn rand() -> usize {
+    return unsafe { (_rdtsc() * _rdtsc() + 998244353_u64 * _rdtsc()) as usize };
+}