Kernel: Add getpeername() syscall, and fix getsockname() behavior.

We were copying the raw IPv4 addresses into the wrong part of sockaddr_in,
and we didn't set sa_family or sa_port.

LibC/sys/socket.cpp

@@ -1,6 +1,8 @@
 #include <sys/socket.h>
 #include <errno.h>
 #include <Kernel/Syscall.h>
+#include <AK/Assertions.h>
+#include <stdio.h>
 
 extern "C" {
 
@@ -78,4 +80,10 @@ int getsockname(int sockfd, struct sockaddr* addr, socklen_t* addrlen)
     __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
+int getpeername(int sockfd, struct sockaddr* addr, socklen_t* addrlen)
+{
+    int rc = syscall(SC_getpeername, sockfd, addr, addrlen);
+    __RETURN_WITH_ERRNO(rc, rc, -1);
+}
+
 }