Add local network scanning feature (ARP)

src/CMakeLists.txt

@@ -116,8 +116,6 @@ set(sources
  daemon.h
  datastructure.c
  datastructure.h
- dhcp-discover.c
- dhcp-discover.h
  dnsmasq_interface.c
  dnsmasq_interface.h
  edns0.c
@@ -180,6 +178,7 @@ add_executable(pihole-FTL
  $<TARGET_OBJECTS:lua>
  $<TARGET_OBJECTS:tre-regex>
  $<TARGET_OBJECTS:syscalls>
+ $<TARGET_OBJECTS:tools>
  )
 if(STATIC STREQUAL "true")
  set_target_properties(pihole-FTL PROPERTIES LINK_SEARCH_START_STATIC ON)
@@ -253,3 +252,4 @@ add_subdirectory(lua)
 add_subdirectory(lua/scripts)
 add_subdirectory(tre-regex)
 add_subdirectory(syscalls)
+add_subdirectory(tools)

src/args.c

@@ -33,7 +33,9 @@
 // LUA dependencies
 #include "lua/ftl_lua.h"
 // run_dhcp_discover()
-#include "dhcp-discover.h"
+#include "tools/dhcp-discover.h"
+// run_arp_scan()
+#include "tools/arp-scan.h"
 // defined in dnsmasq.c
 extern void print_dnsmasq_version(const char *yellow, const char *green, const char *bold, const char *normal);
 
@@ -163,6 +165,24 @@ void parse_args(int argc, char* argv[])
  (argc > 1 && strEndsWith(argv[1], ".db")))
  exit(sqlite3_shell_main(argc, argv));
 
+ // DHCP discovery mode
+ if(argc > 1 && strcmp(argv[1], "dhcp-discover") == 0)
+ {
+ // Enable stdout printing
+ cli_mode = true;
+ exit(run_dhcp_discover());
+ }
+
+ // ARP scanning mode
+ if(argc > 1 && strcmp(argv[1], "arp-scan") == 0)
+ {
+ // Enable stdout printing
+ cli_mode = true;
+ const bool scan_all = argc > 2 && strcmp(argv[2], "-a") == 0;
+ const bool extreme_mode = argc > 2 && strcmp(argv[2], "-x") == 0;
+ exit(run_arp_scan(scan_all, extreme_mode));
+ }
+
  // start from 1, as argv[0] is the executable name
  for(int i = 1; i < argc; i++)
  {
@@ -415,14 +435,6 @@ void parse_args(int argc, char* argv[])
  }
  }
 
- // Regex test mode
- if(strcmp(argv[i], "dhcp-discover") == 0)
- {
- // Enable stdout printing
- cli_mode = true;
- exit(run_dhcp_discover());
- }
-
  // List of implemented arguments
  if(strcmp(argv[i], "-h") == 0 || strcmp(argv[i], "help") == 0 || strcmp(argv[i], "--help") == 0)
  {
@@ -495,13 +507,19 @@ void parse_args(int argc, char* argv[])
 
  printf("%sDebugging and special use:%s\n", yellow, normal);
  printf("\t%sd%s, %sdebug%s Enter debugging mode\n", green, normal, green, normal);
- printf("\t%stest%s Don't start pihole-FTL but\n", green, normal);
- printf("\t instead quit immediately\n");
+ printf("\t%stest%s Don't start pihole-FTL but instead\n", green, normal);
+ printf("\t quit immediately\n");
  printf("\t%s-f%s, %sno-daemon%s Don't go into daemon mode\n\n", green, normal, green, normal);
 
  printf("%sOther:%s\n", yellow, normal);
  printf("\t%sdhcp-discover%s Discover DHCP servers in the local\n", green, normal);
  printf("\t network\n");
+ printf("\t%sarp-scan %s[-a/-x]%s Use ARP to scan local network for\n", green, cyan, normal);
+ printf("\t possible IP conflicts\n");
+ printf("\t Append %s-a%s to force scan on all\n", cyan, normal);
+ printf("\t interfaces\n");
+ printf("\t Append %s-x%s to force scan on all\n", cyan, normal);
+ printf("\t interfaces and scan 10x more often\n");
  printf("\t%s-h%s, %shelp%s Display this help and exit\n\n", green, normal, green, normal);
  exit(EXIT_SUCCESS);
  }

src/capabilities.c

@@ -21,6 +21,47 @@ static const unsigned int capabilityIDs[] = { CAP_CHOWN , CAP_DAC_OVERRIDE ,
 static const char* capabilityNames[] = {"CAP_CHOWN", "CAP_DAC_OVERRIDE", "CAP_DAC_READ_SEARCH", "CAP_FOWNER", "CAP_FSETID", "CAP_KILL", "CAP_SETGID", "CAP_SETUID", "CAP_SETPCAP", "CAP_LINUX_IMMUTABLE", "CAP_NET_BIND_SERVICE", "CAP_NET_BROADCAST", "CAP_NET_ADMIN", "CAP_NET_RAW", "CAP_IPC_LOCK", "CAP_IPC_OWNER", "CAP_SYS_MODULE", "CAP_SYS_RAWIO", "CAP_SYS_CHROOT", "CAP_SYS_PTRACE", "CAP_SYS_PACCT", "CAP_SYS_ADMIN", "CAP_SYS_BOOT", "CAP_SYS_NICE", "CAP_SYS_RESOURCE", "CAP_SYS_TIME", "CAP_SYS_TTY_CONFIG", "CAP_MKNOD", "CAP_LEASE", "CAP_AUDIT_WRITE", "CAP_AUDIT_CONTROL", "CAP_SETFCAP"};
 static const unsigned int numCaps = sizeof(capabilityIDs) / sizeof(*capabilityIDs);
 
+bool check_capability(const unsigned int cap)
+{
+ // First assume header version 1
+ int capsize = 1; // VFS_CAP_U32_1
+ cap_user_data_t data = NULL;
+ cap_user_header_t hdr = calloc(sizeof(*hdr), capsize);
+
+ // Determine capabilities version used by the current kernel
+ capget(hdr, NULL);
+
+ // Check version
+ if (hdr->version != LINUX_CAPABILITY_VERSION_1)
+ {
+ // If unknown version, use largest supported version (3)
+ // Version 2 is deprecated according to linux/capability.h
+ if (hdr->version != LINUX_CAPABILITY_VERSION_2)
+ {
+ hdr->version = LINUX_CAPABILITY_VERSION_3;
+ capsize = 2; // VFS_CAP_U32_3
+ }
+ else
+ {
+ // Use version 2
+ capsize = 2; // VFS_CAP_U32_2
+ }
+ }
+
+ // Get current capabilities
+ data = calloc(sizeof(*data), capsize);
+ capget(hdr, data);
+
+ // Check if the capability is available
+ const bool available = ((data->permitted & (1 << cap)) && (data->effective & (1 << cap)));
+
+ // Free memory
+ free(hdr);
+ free(data);
+
+ return available;
+}
+
 bool check_capabilities(void)
 {
  // First assume header version 1

src/capabilities.h

@@ -10,6 +10,7 @@
 #ifndef CAPABILITIES_H
 #define CAPABILITIES_H
 
+bool check_capability(const unsigned int cap);
 bool check_capabilities(void);
 
 #endif //CAPABILITIES_H

src/syscalls/recvfrom.c

@@ -32,11 +32,14 @@ ssize_t FTLrecvfrom(int sockfd, void *buf, size_t len, int flags, struct sockadd
  // Backup errno value
  const int _errno = errno;
 
- // Final error checking (may have failed for some other reason then an
- // EINTR = interrupted system call)
- if(ret < 0)
+ // Final error checking. May have failed for some other reason then an
+ // EINTR = interrupted system call. In that case, log a warning However,
+ // if the error is EAGAIN, this is not an error, but just a non-blocking
+ // socket that has no data available or we ran into an (expected)
+ // timeout. In that case, do not log a warning
+ if(ret < 0 && errno != EAGAIN)
  logg("WARN: Could not recvfrom() in %s() (%s:%i): %s",
- func, file, line, strerror(errno));
+   func, file, line, strerror(errno));
 
  // Restore errno value
  errno = _errno;

src/syscalls/sendto.c

@@ -33,8 +33,8 @@ ssize_t FTLsendto(int sockfd, void *buf, size_t len, int flags, const struct soc
  const int _errno = errno;
 
  // Final error checking (may have failed for some other reason then an
- // EINTR = interrupted system call)
- if(ret < 0)
+ // EINTR = interrupted system call), also ignore EPROTONOSUPPORT (ARP scanning)
+ if(ret < 0 && errno != EPROTONOSUPPORT)
  logg("WARN: Could not sendto() in %s() (%s:%i): %s",
  func, file, line, strerror(errno));
 

src/tools/CMakeLists.txt

@@ -0,0 +1,20 @@
+# Pi-hole: A black hole for Internet advertisements
+# (c) 2020 Pi-hole, LLC (https://pi-hole.net)
+# Network-wide ad blocking via your own hardware.
+#
+# FTL Engine
+# /src/tools/CMakeList.txt
+#
+# This file is copyright under the latest version of the EUPL.
+# Please see LICENSE file for your rights under this license.
+
+set(tools_sources
+ arp-scan.c
+ arp-scan.h
+ dhcp-discover.c
+ dhcp-discover.h
+ )
+
+add_library(tools OBJECT ${tools_sources})
+target_compile_options(tools PRIVATE "${EXTRAWARN}")
+target_include_directories(tools PRIVATE ${PROJECT_SOURCE_DIR}/src)