Utilities: Add simple traceroute utility

This utility traces the route packets take to a user specified host.

QEMU user networking (the type of networking we currently have setup)
does not support sending "real" raw IPv4 packets, and as such we cant
specify a custom TTL value. As a result, this utility will only work
on real hardware, qemu setup with tun networking (requires root) and
other hypervisors that support bridged adapters (VirtualBox/VMWare).

Meta/build-root-filesystem.sh

@@ -56,6 +56,7 @@ chmod 0400 mnt/boot/Kernel
 chmod 4750 mnt/bin/su
 chmod 4755 mnt/bin/passwd
 chmod 4755 mnt/bin/ping
+chmod 4755 mnt/bin/traceroute
 chmod 4750 mnt/bin/reboot
 chmod 4750 mnt/bin/shutdown
 chmod 4750 mnt/bin/keymap

Userland/Utilities/traceroute.cpp

@@ -0,0 +1,178 @@
+/*
+ * Copyright (c) 2021, Idan Horowitz <idan.horowitz@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/String.h>
+#include <LibCore/ArgsParser.h>
+#include <LibCore/ElapsedTimer.h>
+#include <arpa/inet.h>
+#include <netdb.h>
+#include <netinet/in.h>
+#include <netinet/ip_icmp.h>
+#include <serenity.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+int main(int argc, char** argv)
+{
+    if (pledge("stdio id inet unix", nullptr) < 0) {
+        perror("pledge");
+        return 1;
+    }
+
+    const char* host_name;
+    int max_hops = 30;
+    int max_retries = 3;
+    int echo_timeout = 5;
+
+    Core::ArgsParser args_parser;
+    args_parser.add_positional_argument(host_name, "destination", "destination", Core::ArgsParser::Required::Yes);
+    args_parser.add_option(max_hops, "use at most <hops> to the destination", "max-hops", 'h', "hops");
+    args_parser.add_option(max_retries, "retry TTL at most <tries> times", "max-retries", 'r', "tries");
+    args_parser.add_option(echo_timeout, "wait at most <seconds> for a response", "timeout", 't', "seconds");
+    args_parser.parse(argc, argv);
+
+    if (max_hops < 1 || max_hops > 255) {
+        warnln("Invalid maximum hops amount");
+        return 1;
+    }
+
+    if (max_retries < 1) {
+        warnln("Invalid maximum retries amount");
+        return 1;
+    }
+
+    auto* hostent = gethostbyname(host_name);
+    if (!hostent) {
+        warnln("Lookup failed for '{}'", host_name);
+        return 1;
+    }
+    sockaddr_in host_address {};
+    memset(&host_address, 0, sizeof(host_address));
+    host_address.sin_family = AF_INET;
+    host_address.sin_port = 44444;
+    host_address.sin_addr.s_addr = *(const in_addr_t*)hostent->h_addr_list[0];
+
+    int fd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
+    if (fd < 0) {
+        perror("socket");
+        return 1;
+    }
+
+    if (setgid(getgid()) || setuid(getuid())) {
+        warnln("Failed to drop privileges");
+        return 1;
+    }
+
+    if (pledge("stdio inet unix", nullptr) < 0) {
+        perror("pledge");
+        return 1;
+    }
+
+    timeval timeout { echo_timeout, 0 };
+    if (setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(timeout)) < 0) {
+        perror("setsockopt");
+        return 1;
+    }
+
+    struct icmp_request {
+        struct icmphdr header;
+        char msg[64 - sizeof(struct icmphdr)];
+    };
+
+    struct icmp_response {
+        u8 ip_header[20];
+        struct icmphdr header;
+        char msg[64 - sizeof(struct icmphdr)];
+    };
+
+    // 1: reached target
+    // 0: got ttl exhausted response
+    // -1: error or no response
+    auto try_reach_host = [&](int ttl) -> int {
+        Core::ElapsedTimer m_timer { true };
+        for (auto i = 0; i < max_retries; i++) {
+            icmp_request request {};
+            request.header = { ICMP_ECHO, 0, 0, { { 0, 0 } } };
+            bool fits = String::number(ttl).copy_characters_to_buffer(request.msg, sizeof(request.msg));
+            VERIFY(fits);
+            request.header.checksum = internet_checksum(&request, sizeof(request));
+
+            m_timer.start();
+            if (sendto(fd, &request, sizeof(request), 0, (sockaddr*)&host_address, sizeof(host_address)) < 0)
+                return -1;
+
+            icmp_response response {};
+            sockaddr_in peer_address {};
+            memset(&peer_address, 0, sizeof(peer_address));
+            size_t peer_address_size = sizeof(peer_address);
+            int result = recvfrom(fd, &response, sizeof(response), 0, (sockaddr*)&peer_address, (socklen_t*)&peer_address_size);
+            if (result < 0) {
+                if (result == EAGAIN)
+                    return -1;
+                continue;
+            }
+
+            if (response.header.type != ICMP_ECHOREPLY && response.header.type != ICMP_TIME_EXCEEDED)
+                continue;
+
+            auto* peer = gethostbyaddr(&peer_address.sin_addr, sizeof(peer_address.sin_addr), AF_INET);
+
+            String peer_name;
+            if (peer) {
+                peer_name = peer->h_name;
+            } else {
+                char addr_buf[INET_ADDRSTRLEN];
+                peer_name = inet_ntop(AF_INET, &peer_address.sin_addr, addr_buf, sizeof(addr_buf));
+            }
+            outln("{:2}:  {:50}  {:4}ms", ttl, peer_name, m_timer.elapsed());
+
+            if (response.header.type == ICMP_TIME_EXCEEDED)
+                return 0;
+            if (response.header.type == ICMP_ECHOREPLY)
+                return 1;
+        }
+        return -1;
+    };
+
+    for (auto ttl = 1; ttl <= max_hops; ttl++) {
+        if (setsockopt(fd, IPPROTO_IP, IP_TTL, &ttl, sizeof(ttl)) < 0) {
+            perror("setsockopt");
+            return 1;
+        }
+
+        int result = try_reach_host(ttl);
+        if (result < 0) {
+            outln("{:2}:  no reply", ttl);
+        } else if (result == 1) {
+            outln("     Hops: {}", ttl);
+            return 0;
+        }
+    }
+    outln("     Too many hops: {}", max_hops);
+    return 0;
+}