Basic traceroute

.clang-format

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+---
+Language:        Cpp
+# BasedOnStyle:  Google
+AccessModifierOffset: -1
+AlignAfterOpenBracket: Align
+AlignConsecutiveAssignments: false
+AlignConsecutiveDeclarations: false
+AlignEscapedNewlines: Left
+AlignOperands:   true
+AlignTrailingComments: true
+AllowAllParametersOfDeclarationOnNextLine: true
+AllowShortBlocksOnASingleLine: false
+AllowShortCaseLabelsOnASingleLine: false
+AllowShortFunctionsOnASingleLine: All
+AllowShortIfStatementsOnASingleLine: true
+AllowShortLoopsOnASingleLine: true
+AlwaysBreakAfterDefinitionReturnType: None
+AlwaysBreakAfterReturnType: None
+AlwaysBreakBeforeMultilineStrings: true
+AlwaysBreakTemplateDeclarations: true
+BinPackArguments: true
+BinPackParameters: true
+BraceWrapping:   
+  AfterClass:      false
+  AfterControlStatement: false
+  AfterEnum:       false
+  AfterFunction:   false
+  AfterNamespace:  false
+  AfterObjCDeclaration: false
+  AfterStruct:     false
+  AfterUnion:      false
+  AfterExternBlock: false
+  BeforeCatch:     false
+  BeforeElse:      false
+  IndentBraces:    false
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+  SplitEmptyRecord: true
+  SplitEmptyNamespace: true
+BreakBeforeBinaryOperators: None
+BreakBeforeBraces: Attach
+BreakBeforeInheritanceComma: false
+BreakBeforeTernaryOperators: true
+BreakConstructorInitializersBeforeComma: false
+BreakConstructorInitializers: BeforeColon
+BreakAfterJavaFieldAnnotations: false
+BreakStringLiterals: true
+ColumnLimit:     80
+CommentPragmas:  '^ IWYU pragma:'
+CompactNamespaces: false
+ConstructorInitializerAllOnOneLineOrOnePerLine: true
+ConstructorInitializerIndentWidth: 4
+ContinuationIndentWidth: 4
+Cpp11BracedListStyle: true
+DerivePointerAlignment: true
+DisableFormat:   false
+ExperimentalAutoDetectBinPacking: false
+FixNamespaceComments: true
+ForEachMacros:   
+  - foreach
+  - Q_FOREACH
+  - BOOST_FOREACH
+IncludeBlocks:   Preserve
+IncludeCategories: 
+  - Regex:           '^<ext/.*\.h>'
+    Priority:        2
+  - Regex:           '^<.*\.h>'
+    Priority:        1
+  - Regex:           '^<.*'
+    Priority:        2
+  - Regex:           '.*'
+    Priority:        3
+IncludeIsMainRegex: '([-_](test|unittest))?$'
+IndentCaseLabels: true
+IndentPPDirectives: None
+IndentWidth:     2
+IndentWrappedFunctionNames: false
+JavaScriptQuotes: Leave
+JavaScriptWrapImports: true
+KeepEmptyLinesAtTheStartOfBlocks: false
+MacroBlockBegin: ''
+MacroBlockEnd:   ''
+MaxEmptyLinesToKeep: 1
+NamespaceIndentation: None
+ObjCBlockIndentWidth: 2
+ObjCSpaceAfterProperty: false
+ObjCSpaceBeforeProtocolList: false
+PenaltyBreakAssignment: 2
+PenaltyBreakBeforeFirstCallParameter: 1
+PenaltyBreakComment: 300
+PenaltyBreakFirstLessLess: 120
+PenaltyBreakString: 1000
+PenaltyExcessCharacter: 1000000
+PenaltyReturnTypeOnItsOwnLine: 200
+PointerAlignment: Left
+RawStringFormats: 
+  - Delimiter:       pb
+    Language:        TextProto
+    BasedOnStyle:    google
+ReflowComments:  true
+SortIncludes:    true
+SortUsingDeclarations: true
+SpaceAfterCStyleCast: false
+SpaceAfterTemplateKeyword: true
+SpaceBeforeAssignmentOperators: true
+SpaceBeforeParens: ControlStatements
+SpaceInEmptyParentheses: false
+SpacesBeforeTrailingComments: 2
+SpacesInAngles:  false
+SpacesInContainerLiterals: true
+SpacesInCStyleCastParentheses: false
+SpacesInParentheses: false
+SpacesInSquareBrackets: false
+Standard:        Auto
+TabWidth:        8
+UseTab:          Never
+...
+

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.16)
+project(nettools)
+
+set(CMAKE_CXX_STANDARD 14)
+
+add_executable(nettools main.cpp)

main.cpp

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+#include <arpa/inet.h>
+#include <netdb.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/ip_icmp.h>
+#include <sys/socket.h>
+#include <cstring>
+#include <iostream>
+
+int main() {
+  int send_socket;
+  send_socket = socket(PF_INET, SOCK_DGRAM, 0);
+  if (send_socket < 0) {
+    std::cerr << "Error opening socket for sending";
+    return 1;
+  }
+
+  int receive_socket;
+  receive_socket = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
+  if (receive_socket < 0) {
+    std::cerr << "Error opening socket for receiving";
+    return 1;
+  }
+
+  const char ip_cstring[]{"172.217.19.78"};
+  in_addr ip;
+  if (!inet_aton(ip_cstring, &ip)) {
+    std::cerr << "Failed to parse IP address " << ip_cstring << '\n';
+    return 1;
+  }
+
+  hostent *remote_host;
+  remote_host = gethostbyaddr((const void *)&ip, sizeof(ip), AF_INET);
+  if (!remote_host) {
+    std::cerr << "Failed to get host by address\n";
+    return 1;
+  }
+
+  const char port_cstring[]{"80"};
+  int port = atoi(port_cstring);
+
+  sockaddr_in remote_address;
+  memset((char *)&remote_address, 0, sizeof(remote_address));
+  remote_address.sin_family = AF_INET;
+  memcpy((void *)&remote_address.sin_addr, remote_host->h_addr,
+         remote_host->h_length);
+  remote_address.sin_port = htons(port);
+
+  for (int ttl{0}; ttl < 20; ++ttl) {
+    setsockopt(send_socket, IPPROTO_IP, IP_TTL, &ttl, sizeof(ttl));
+
+    char message[]{"hello"};
+    if (sendto(send_socket, message, strlen(message), 0,
+               (sockaddr *)&remote_address, sizeof(remote_address)) < 0) {
+      std::cerr << "Failed to send\n";
+      return 1;
+    }
+    std::cout << "sent\n";
+
+    char buffer[2048];
+    int received_length{};
+    sockaddr_in received_addr;
+    socklen_t received_addr_size{sizeof(received_addr)};
+    std::cout << "Listening...\n";
+    received_length = recvfrom(receive_socket, buffer, 2047, 0,
+                               (sockaddr *)&received_addr, &received_addr_size);
+    std::cout << "Received something of length " << received_length << ":\n";
+
+    iphdr *ip_hdr = reinterpret_cast<iphdr *>(buffer);
+    in_addr source, dest;
+    source.s_addr = ip_hdr->saddr;
+    dest.s_addr = ip_hdr->daddr;
+    std::cout << "IP header length is " << ip_hdr->ihl * 4 << " bytes\n"
+              << "ttl=" << static_cast<int>(ip_hdr->ttl) << '\n'
+              << "source=" << inet_ntoa(source) << '\n'
+              << "destination=" << inet_ntoa(dest) << '\n'
+              << '\n';
+
+    icmphdr *icmp_hdr =
+        reinterpret_cast<icmphdr *>((char *)ip_hdr + (4 * ip_hdr->ihl));
+    std::cout << "ICMP msgtype=" << static_cast<int>(icmp_hdr->type) << '\n'
+              << "code=" << static_cast<int>(icmp_hdr->code) << '\n'
+              << "checksum=" << static_cast<int>(icmp_hdr->checksum) << '\n'
+              << '\n';
+  }
+
+  return 0;
+}