Add libpcap example for low level operation.

pcapio/.gitignore

+# This file is used to ignore files which are generated
+# ----------------------------------------------------------------------------
+
+*~
+*.autosave
+*.a
+*.core
+*.moc
+*.o
+*.obj
+*.orig
+*.rej
+*.so
+*.so.*
+*_pch.h.cpp
+*_resource.rc
+*.qm
+.#*
+*.*#
+core
+!core/
+tags
+.DS_Store
+.directory
+*.debug
+Makefile*
+*.prl
+*.app
+moc_*.cpp
+ui_*.h
+qrc_*.cpp
+Thumbs.db
+*.res
+*.rc
+/.qmake.cache
+/.qmake.stash
+
+# qtcreator generated files
+*.pro.user*
+
+# xemacs temporary files
+*.flc
+
+# Vim temporary files
+.*.swp
+
+# Visual Studio generated files
+*.ib_pdb_index
+*.idb
+*.ilk
+*.pdb
+*.sln
+*.suo
+*.vcproj
+*vcproj.*.*.user
+*.ncb
+*.sdf
+*.opensdf
+*.vcxproj
+*vcxproj.*
+
+# MinGW generated files
+*.Debug
+*.Release
+
+# Python byte code
+*.pyc
+
+# Binaries
+# --------
+*.dll
+*.exe
+

pcapio/CMakeLists.txt

+cmake_minimum_required(VERSION 3.5)
+
+project(pcapio LANGUAGES CXX)
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+set (PRJ_HEADERS
+    pcapio.h
+)
+
+set (PRJ_SOURCES
+    pcapio.cpp
+)
+add_executable(pcapio
+    ${PRJ_HEADERS}
+    ${PRJ_SOURCES}
+    main.cpp
+)
+
+target_link_libraries(pcapio pcap)

pcapio/main.cpp

+#include <iostream>
+#include "pcapio.h"
+#include <pcap.h>
+using namespace std;
+
+int main()
+{
+	std::map<std::string,std::string > devmap;
+	std::string errstring = PCAPIO::pcapio_interfaces(devmap);
+	for (auto & p : devmap)
+	{
+		cout <<p.second;
+		cout <<"\n";
+	}
+
+	cout <<"Input device name:";
+
+	std::string strDev;
+	cin >> strDev;
+
+	pcap_t *handle = NULL;
+	char errbuf[PCAP_ERRBUF_SIZE];
+	handle = pcap_open_live(strDev.c_str(), 65535, 1, 10, errbuf);
+	if(handle == NULL)
+	{
+		printf("pcap_open_live return err,errbuf:%s...\n", errbuf);
+		return -1;
+	}
+	struct bpf_program filter;
+	char filter_app[] = "ip";
+	bpf_u_int32 net = 0;
+	int ret32 = pcap_compile(handle, &filter, filter_app, 0, net);
+	if(ret32 < 0)
+	{
+		printf("pcap_compile return %d, errbuf:%s\n", ret32, errbuf);
+		return -1;
+	}
+	ret32 = pcap_setfilter(handle, &filter);
+	if(ret32 < 0)
+	{
+		printf("pcap_setfilter return %d, errbuf:%s\n", ret32, errbuf);
+		return -1;
+	}
+
+	const u_char *packet;
+	struct pcap_pkthdr header;
+
+	pcap_set_buffer_size(handle,128*1024*1024);
+
+
+	while (1)
+	{
+		packet = pcap_next(handle, &header);
+		if(packet)
+		{
+			printf("LEN=%d:", header.len);
+			for (int i=0;i<header.len;++i)
+			{
+				if ((i>=14 && i<32) || i+4 >= header.len)
+					printf ("%02X",packet[i]);
+				else if (i==32)
+					printf ("...");
+			}
+			printf ("\n");
+		}
+	}
+	pcap_close(handle);
+	return 0;
+}

pcapio/pcapio.cpp

+#include "pcapio.h"
+#include <pcap.h>
+#include <string.h>
+namespace PCAPIO{
+	std::string ifaddresses(pcap_if_t *d);
+
+	std::string pcapio_interfaces(std::map<std::string,std::string> & devmap)
+	{
+		std::string res;
+		pcap_if_t *alldevs;
+		int count = 0;
+		char errbuf[PCAP_ERRBUF_SIZE];
+		if(pcap_findalldevs(&alldevs, errbuf) == -1){
+			res = errbuf;
+			return res;
+		}
+		for(auto d = alldevs; d != NULL; d = d->next){
+			std::string d_name = d->name;
+			std::string d_des = ifaddresses(d);
+			devmap[d_name] = d_des;
+		}
+
+		pcap_freealldevs(alldevs);
+		return res;
+	}
+	std::string address_print(unsigned char * v)
+	{
+		std::string res;
+		char buf[1024];
+		int lbegin = 0, rbegin = 13;
+		while (!v[lbegin] )
+		{
+			++lbegin;
+			if (lbegin >=rbegin)
+				break;
+		}
+		while (!v[rbegin] )
+		{
+			--rbegin;
+			if (lbegin >=rbegin)
+				break;
+		}
+		res += "HEX(";
+		for (int i =lbegin; i<=rbegin;++i)
+		{
+			snprintf(buf,1024,"%02X", (unsigned int)v[i]);
+			res += buf;
+		}
+		res += ")";
+		res += "DEC(";
+		for (int i =lbegin; i<=rbegin;++i)
+		{
+			if (i>lbegin)
+				res += ".";
+			snprintf(buf,1024,"%u", (unsigned int)v[i] );
+			res += buf;
+		}
+		res += ")";
+
+		return res;
+	}
+	/* Print all the available information on the given interface */
+	std::string ifaddresses(pcap_if_t *d)
+	{
+		char buf[1024];
+		pcap_addr_t *a;
+		std::string res = d->name;
+		res += "\n";
+		if(d->description)
+		{
+			res += d->description;
+			res += "\n";
+		}
+
+		for(a=d->addresses;a;a=a->next) {
+			snprintf(buf,1024,"\tAF_0x%02X:",(unsigned int)a->addr->sa_family);
+			res += buf;
+			if (a->addr)
+			{
+				snprintf(buf,1024,"\n\t\tAddr:%s ",address_print((unsigned char *)a->addr->sa_data).c_str());
+				res += buf;
+			}
+			if (a->netmask)
+			{
+				snprintf(buf,1024,"\n\t\tMask:%s ",address_print((unsigned char *)a->addr->sa_data).c_str());
+				res += buf;
+			}
+			if (a->broadaddr)
+			{
+				snprintf(buf,1024,"\n\t\tCast:%s ",address_print((unsigned char *)a->addr->sa_data).c_str());
+				res += buf;
+			}
+			if (a->dstaddr)
+			{
+				snprintf(buf,1024,"\n\t\tDest:%s ",address_print((unsigned char *)a->addr->sa_data).c_str());
+				res += buf;
+			}
+			res += "\n";
+		}
+		return res;
+	}
+}
+

pcapio/pcapio.h

+#ifndef PCAPIO_H
+#define PCAPIO_H
+#include <string>
+#include <map>
+
+namespace PCAPIO{
+
+	std::string pcapio_interfaces(std::map<std::string,std::string> & devmap);
+
+
+}
+
+#endif // PCAPIO_H