之前,我们实现了用dpdk处理udp协议数据。这里,我们在udp基础上实现dns,其实是借用了开源框架,懒得自己去实现解析了。
这里我们没有使用自己实现的arp,而是把arp包交给kni处理。为什么辛辛苦苦实现arp,最后却不用呢?因为我们没有实现记录arp的功能,网卡在接收到arp包后,给发送方回了arp包,但是自己却没有处理这个包。arp表上没有相应ip与mac的映射,那就发送不了数据,kni会帮我们添加arp表项。
使用kni,又会有一个问题,kni默认是不进行回环的,也就是说,接受到了数据不会回发。设置kni回发,有三种方法。
法一:修改/sys/devices/virtual/net/%s/carrier
echo 1 > /sys/devices/virtual/net/%s/carrier
法二:在dpdk目录下的x86_64-native-linux-gcc/kmod路径下
insmod rte_kni.ko carrier=on # 注意root
法三:代码中调用rte_kni_update_link()函数,该函数的核心功能就是将1写入/sys/devices/virtual/net/%s/carrier
文件。
在代码中,我们使用第三种方法。
while (1) {
rte_delay_ms(500);
memset(&link, 0, sizeof(link));
rte_eth_link_get_nowait(g_dpdkPortId, &link);
prev = rte_kni_update_link(kni, link.link_status);
// echo 1 > /sys/devices/virtual/net/vEth0/carrier
log_link_state(kni, prev, &link);
}
由于/sys/devices/virtual/net/%s/carrier
值是公共资源,为了避免被其他进程修改,这里开了一个线程,每隔500ms检测并修改值为1。
//main函数中
pthread_t kni_link_tid;
int ret = rte_ctrl_thread_create(&kni_link_tid,
"KNI link status check", NULL,
monitor_all_ports_link_status, NULL);
if (ret < 0)
rte_exit(EXIT_FAILURE, "Could not create link status thread!\n");
介绍两个dns工具。
dig(domain information group)是常用的域名查询工具,可以从DNS域名服务器查询主机地址信息,获取到详细的域名信息。这个命令是Bind的一部分,本身并没有在Windows和Linux系统中集成,所以如果我们想要使用该命令就需要先下载相应的软件包。
apt-get install dnsutils
查询记录的类型
dig www.baidu.com A # 查询A记录,如果域名后面不加任何参数,默认查询A记录
dig www.baidu.com MX # 查询MX记录
dig www.baidu.com CNAME # 查询CNAME记录
dig www.baidu.com NS # 查询NS记录
dig www.baidu.com ANY # 查询上面所有的记录
dig www.baidu.com A +short # 查询A记录并显示简要的返回的结果
dig www.baidu.com A +multiline # 查询A记录并显示详细的返回结果
查询指定dns服务器
dig @192.168.0.2 www.baidu.com # 表示从192.168.0.2这个IP服务器对www.baidu.com进行A记录查询
若不指定DNS服务器,dig会依次使用/etc/resolv.conf里的地址作为DNS服务器。
以查询百度域名为例
dig www.baidu.com
下面是输出的结果,注释是后加的,为了方便解释。
# 这部分输出版本信息(version 9.10.3)和全局的设置选项
; <<>> DiG 9.10.3-P4-Ubuntu <<>> www.baidu.com
;; global options: +cmd
# 这部分输出从DNS返回的技术信息,比较重要的是 status,如果 status 的值为 NOERROR ,则说明本次查询成功
# 这段信息可以用选项 [no]comments 来控制是否显示,但是小心禁止掉comments也可能关闭一些其它的选项
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 5575
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
# 查询字段,显示了我们要查询的域名以及查询的服务,A表示的是A记录查询,即主机查询
;; QUESTION SECTION:
;www.baidu.com. IN A
# 这一部分是DNS服务器的答复
# 显示www.baidu.com.有一个CNAME记录,以及www.a.shifen.com.有两个A记录
# 415、146是TTL值,表示缓存时间,即415s内不用重新查询
;; ANSWER SECTION:
www.baidu.com. 415 IN CNAME www.a.shifen.com.
www.a.shifen.com. 146 IN A 14.215.177.38
www.a.shifen.com. 146 IN A 14.215.177.39
# 这部分显示了请求所花的时间,dns服务器和端口,当前时间,以及查询信息的大小
;; Query time: 2 msec
;; SERVER: 192.168.2.1#53(192.168.2.1)
;; WHEN: Sat Sep 03 01:39:18 PDT 2022
;; MSG SIZE rcvd: 104
当然,dig还有一些其他的命令操作,但是在这里介绍这些已经够用了。
再介绍另一个工具
DNSPerf(DNS Performance)是一款dns压力测试工具,从全世界超过两百个城市节点来检测各个 DNS 速度、反应时间及上线率(Uptime),除此之外,DNSPerf 还有针对一般使用者会用到的开放式 DNS 解析服务(Public DNS)进行监测记录。
命令安装
apt-get install dnsperf
也可以源码安装,github地址https://github.com/cobblau/dnsperf
dnsperf 支持下面的这些命令行参数
-s 用来指定DNS服务器的IP地址,默认值是127.0.0.1
-p 用来指定DNS服务器的端口,默认值是53
-d 用来指定DNS消息的内容文件,该文件中包含要探测的域名和资源记录类型
-t 用来指定每个请求的超时时间,默认值是3000ms
-Q 用来指定本次压测的最大请求数,默认值是1000
-c 用来指定并发探测数,默认值是100. dnsperf会从-d指定的文件中随机选取100个座位探测域名来发送DNS请求
-l 用来指定本次压测的时间,默认值是无穷大
-e 本选项通过EDNS0,在OPT资源记录中运用edns-client-subnet来指定真实的client ip
-i 用来指定前后探测的时间间隔,因为dnsperf是一个压测工具,所以本选项目前还不支持
-P 指定用哪个传输层协议发送DNS请求,udp或者tcp。默认值是udp
-f 指定用什么地址类型发送DNS请求,inet或者inet6。默认值是inet
-v 除了标准的输出外,还输出每个相应码的个数
-h 打印帮助
在使用之前,还需要写一个文档
# vi testfile,在testfile中
www.baidu.com A
执行命令
./src/dnsperf -d tsetfile -s 192.168.0.2 -c10000 -Q10000 -l60
执行结果
DNS Performance Testing Tool
[Status] Processing query data
[Status] Sending queries to 127.0.0.1:53
time up
[Status]DNS Query Performance Testing Finish
[Result]Quries sent: 35650
[Result]Quries completed: 35578
[Result]Complete percentage: 99.80%
[Result]Elapsed time(s): 1.00000
[Result]Queries Per Second: 35650.0000
这里我们使用simpleDNS框架来实现
先从git下载
https://github.com/mwarning/SimpleDNS.git
然后使用其中的源码,其实是直接拷贝……
#ifndef __DPDK_DNS_H__
#define __DPDK_DNS_H__
/* Response Type */
enum {
Ok_ResponseType = 0,
FormatError_ResponseType = 1,
ServerFailure_ResponseType = 2,
NameError_ResponseType = 3,
NotImplemented_ResponseType = 4,
Refused_ResponseType = 5
};
/* Resource Record Types */
enum {
A_Resource_RecordType = 1,
NS_Resource_RecordType = 2,
CNAME_Resource_RecordType = 5,
SOA_Resource_RecordType = 6,
PTR_Resource_RecordType = 12,
MX_Resource_RecordType = 15,
TXT_Resource_RecordType = 16,
AAAA_Resource_RecordType = 28,
SRV_Resource_RecordType = 33
};
/* Operation Code */
enum {
QUERY_OperationCode = 0, /* standard query */
IQUERY_OperationCode = 1, /* inverse query */
STATUS_OperationCode = 2, /* server status request */
NOTIFY_OperationCode = 4, /* request zone transfer */
UPDATE_OperationCode = 5 /* change resource records */
};
/* Response Code */
enum {
NoError_ResponseCode = 0,
FormatError_ResponseCode = 1,
ServerFailure_ResponseCode = 2,
NameError_ResponseCode = 3
};
/* Query Type */
enum {
IXFR_QueryType = 251,
AXFR_QueryType = 252,
MAILB_QueryType = 253,
MAILA_QueryType = 254,
STAR_QueryType = 255
};
/*
* Types.
*/
/* Question Section */
struct Question {
char *qName;
uint16_t qType;
uint16_t qClass;
struct Question *next; // for linked list
};
/* Data part of a Resource Record */
union ResourceData {
struct {
uint8_t txt_data_len;
char *txt_data;
} txt_record;
struct {
uint8_t addr[4];
} a_record;
struct {
uint8_t addr[16];
} aaaa_record;
};
/* Resource Record Section */
struct ResourceRecord {
char *name;
uint16_t type;
uint16_t class;
uint32_t ttl;
uint16_t rd_length;
union ResourceData rd_data;
struct ResourceRecord *next; // for linked list
};
struct Message {
uint16_t id; /* Identifier */
/* Flags */
uint16_t qr; /* Query/Response Flag */
uint16_t opcode; /* Operation Code */
uint16_t aa; /* Authoritative Answer Flag */
uint16_t tc; /* Truncation Flag */
uint16_t rd; /* Recursion Desired */
uint16_t ra; /* Recursion Available */
uint16_t rcode; /* Response Code */
uint16_t qdCount; /* Question Count */
uint16_t anCount; /* Answer Record Count */
uint16_t nsCount; /* Authority Record Count */
uint16_t arCount; /* Additional Record Count */
/* At least one question; questions are copied to the response 1:1 */
struct Question *questions;
/*
* Resource records to be send back.
* Every resource record can be in any of the following places.
* But every place has a different semantic.
*/
struct ResourceRecord *answers;
struct ResourceRecord *authorities;
struct ResourceRecord *additionals;
};
int decode_msg(struct Message *msg, const uint8_t *buffer, int size);
void resolve_query(struct Message *msg);
int encode_msg(struct Message *msg, uint8_t **buffer);
void free_questions(struct Question *qq);
void free_resource_records(struct ResourceRecord *rr);
void print_message(struct Message *msg);
#endif
再拷实现,注意要把内存操作malloc、free改为rte_前缀的,因为我们是使用dpdk实现的。
/*
* This software is licensed under the CC0.
*
* This is a _basic_ DNS Server for educational use.
* It does not prevent invalid packets from crashing
* the server.
*
* To test start the program and issue a DNS request:
* dig @127.0.0.1 -p 9000 foo.bar.com
*/
/*
* Masks and constants.
*/
static const uint32_t QR_MASK = 0x8000;
static const uint32_t OPCODE_MASK = 0x7800;
static const uint32_t AA_MASK = 0x0400;
static const uint32_t TC_MASK = 0x0200;
static const uint32_t RD_MASK = 0x0100;
static const uint32_t RA_MASK = 0x8000;
static const uint32_t RCODE_MASK = 0x000F;
int get_A_Record(uint8_t addr[4], const char domain_name[])
{
if (strcmp("foo.bar.com", domain_name) == 0) {
addr[0] = 192;
addr[1] = 168;
addr[2] = 232;
addr[3] = 133;
return 0;
} else {
return -1;
}
}
int get_AAAA_Record(uint8_t addr[16], const char domain_name[])
{
if (strcmp("foo.bar.com", domain_name) == 0) {
addr[0] = 0xfe;
addr[1] = 0x80;
addr[2] = 0x00;
addr[3] = 0x00;
addr[4] = 0x00;
addr[5] = 0x00;
addr[6] = 0x00;
addr[7] = 0x00;
addr[8] = 0x00;
addr[9] = 0x00;
addr[10] = 0x00;
addr[11] = 0x00;
addr[12] = 0x00;
addr[13] = 0x00;
addr[14] = 0x00;
addr[15] = 0x01;
return 0;
} else {
return -1;
}
}
int get_TXT_Record(char **addr, const char domain_name[])
{
if (strcmp("foo.bar.com", domain_name) == 0) {
*addr = "abcdefg";
return 0;
} else {
return -1;
}
}
/*
* Debugging functions.
*/
void print_hex(uint8_t *buf, size_t len)
{
int i;
printf("%zu bytes:\n", len);
for (i = 0; i < len; ++i)
printf("%02x ", buf[i]);
printf("\n");
}
void print_resource_record(struct ResourceRecord *rr)
{
int i;
while (rr) {
printf(" ResourceRecord { name '%s', type %u, class %u, ttl %u, rd_length %u, ",
rr->name,
rr->type,
rr->class,
rr->ttl,
rr->rd_length
);
union ResourceData *rd = &rr->rd_data;
switch (rr->type) {
case A_Resource_RecordType:
printf("Address Resource Record { address ");
for(i = 0; i < 4; ++i)
printf("%s%u", (i ? "." : ""), rd->a_record.addr[i]);
printf(" }");
break;
case AAAA_Resource_RecordType:
printf("AAAA Resource Record { address ");
for(i = 0; i < 16; ++i)
printf("%s%02x", (i ? ":" : ""), rd->aaaa_record.addr[i]);
printf(" }");
break;
case TXT_Resource_RecordType:
printf("Text Resource Record { txt_data '%s' }",
rd->txt_record.txt_data
);
break;
default:
printf("Unknown Resource Record { ??? }");
}
printf("}\n");
rr = rr->next;
}
}
void print_message(struct Message *msg)
{
struct Question *q;
printf("QUERY { ID: %02x", msg->id);
printf(". FIELDS: [ QR: %u, OpCode: %u ]", msg->qr, msg->opcode);
printf(", QDcount: %u", msg->qdCount);
printf(", ANcount: %u", msg->anCount);
printf(", NScount: %u", msg->nsCount);
printf(", ARcount: %u,\n", msg->arCount);
q = msg->questions;
while (q) {
printf(" Question { qName '%s', qType %u, qClass %u }\n",
q->qName,
q->qType,
q->qClass
);
q = q->next;
}
print_resource_record(msg->answers);
print_resource_record(msg->authorities);
print_resource_record(msg->additionals);
printf("}\n");
}
/*
* Basic memory operations.
*/
size_t get16bits(const uint8_t **buffer)
{
uint16_t value;
memcpy(&value, *buffer, 2);
*buffer += 2;
return ntohs(value);
}
void put8bits(uint8_t **buffer, uint8_t value)
{
memcpy(*buffer, &value, 1);
*buffer += 1;
}
void put16bits(uint8_t **buffer, uint16_t value)
{
value = htons(value);
memcpy(*buffer, &value, 2);
*buffer += 2;
}
void put32bits(uint8_t **buffer, uint32_t value)
{
value = htonl(value);
memcpy(*buffer, &value, 4);
*buffer += 4;
}
/*
* Deconding/Encoding functions.
*/
// 3foo3bar3com0 => foo.bar.com (No full validation is done!)
char *decode_domain_name(const uint8_t **buf, size_t len)
{
char domain[256];
for (int i = 1; i < MIN(256, len); i += 1) {
uint8_t c = (*buf)[i];
if (c == 0) {
domain[i - 1] = 0;
*buf += i + 1;
return strdup(domain);
} else if (c <= 63) {
domain[i - 1] = '.';
} else {
domain[i - 1] = c;
}
}
return NULL;
}
// foo.bar.com => 3foo3bar3com0
void encode_domain_name(uint8_t **buffer, const char *domain)
{
uint8_t *buf = *buffer;
const char *beg = domain;
const char *pos;
int len = 0;
int i = 0;
while ((pos = strchr(beg, '.'))) {
len = pos - beg;
buf[i] = len;
i += 1;
memcpy(buf+i, beg, len);
i += len;
beg = pos + 1;
}
len = strlen(domain) - (beg - domain);
buf[i] = len;
i += 1;
memcpy(buf + i, beg, len);
i += len;
buf[i] = 0;
i += 1;
*buffer += i;
}
void decode_header(struct Message *msg, const uint8_t **buffer)
{
msg->id = get16bits(buffer);
uint32_t fields = get16bits(buffer);
msg->qr = (fields & QR_MASK) >> 15;
msg->opcode = (fields & OPCODE_MASK) >> 11;
msg->aa = (fields & AA_MASK) >> 10;
msg->tc = (fields & TC_MASK) >> 9;
msg->rd = (fields & RD_MASK) >> 8;
msg->ra = (fields & RA_MASK) >> 7;
msg->rcode = (fields & RCODE_MASK) >> 0;
msg->qdCount = get16bits(buffer);
msg->anCount = get16bits(buffer);
msg->nsCount = get16bits(buffer);
msg->arCount = get16bits(buffer);
}
void encode_header(struct Message *msg, uint8_t **buffer)
{
put16bits(buffer, msg->id);
int fields = 0;
fields |= (msg->qr << 15) & QR_MASK;
fields |= (msg->rcode << 0) & RCODE_MASK;
// TODO: insert the rest of the fields
put16bits(buffer, fields);
put16bits(buffer, msg->qdCount);
put16bits(buffer, msg->anCount);
put16bits(buffer, msg->nsCount);
put16bits(buffer, msg->arCount);
}
int decode_msg(struct Message *msg, const uint8_t *buffer, int size)
{
int i;
decode_header(msg, &buffer);
if (msg->anCount != 0 || msg->nsCount != 0) {
printf("Only questions expected!\n");
return -1;
}
// parse questions
uint32_t qcount = msg->qdCount;
for (i = 0; i < qcount; ++i) {
struct Question *q = rte_malloc("Question", sizeof(struct Question), 0);
q->qName = decode_domain_name(&buffer, size);
q->qType = get16bits(&buffer);
q->qClass = get16bits(&buffer);
if (q->qName == NULL) {
printf("Failed to decode domain name!\n");
return -1;
}
// prepend question to questions list
q->next = msg->questions;
msg->questions = q;
}
// We do not expect any resource records to parse here.
return 0;
}
// For every question in the message add a appropiate resource record
// in either section 'answers', 'authorities' or 'additionals'.
void resolve_query(struct Message *msg)
{
struct ResourceRecord *beg;
struct ResourceRecord *rr;
struct Question *q;
int rc;
// leave most values intact for response
msg->qr = 1; // this is a response
msg->aa = 1; // this server is authoritative
msg->ra = 0; // no recursion available
msg->rcode = Ok_ResponseType;
// should already be 0
msg->anCount = 0;
msg->nsCount = 0;
msg->arCount = 0;
// for every question append resource records
q = msg->questions;
while (q) {
rr = rte_malloc("ResourceRecord", sizeof(struct ResourceRecord), 0); //malloc
memset(rr, 0, sizeof(struct ResourceRecord));
rr->name = strdup(q->qName);
rr->type = q->qType;
rr->class = q->qClass;
rr->ttl = 60*60; // in seconds; 0 means no caching
//printf("Query for '%s'\n", q->qName);
// We only can only answer two question types so far
// and the answer (resource records) will be all put
// into the answers list.
// This behavior is probably non-standard!
switch (q->qType) {
case A_Resource_RecordType:
rr->rd_length = 4;
rc = get_A_Record(rr->rd_data.a_record.addr, q->qName);
if (rc < 0)
{
rte_free(rr->name);
rte_free(rr);
goto next;
}
break;
case AAAA_Resource_RecordType:
rr->rd_length = 16;
rc = get_AAAA_Record(rr->rd_data.aaaa_record.addr, q->qName);
if (rc < 0)
{
rte_free(rr->name);
rte_free(rr);
goto next;
}
break;
case TXT_Resource_RecordType:
rc = get_TXT_Record(&(rr->rd_data.txt_record.txt_data), q->qName);
if (rc < 0) {
rte_free(rr->name);
rte_free(rr);
goto next;
}
int txt_data_len = strlen(rr->rd_data.txt_record.txt_data);
rr->rd_length = txt_data_len + 1;
rr->rd_data.txt_record.txt_data_len = txt_data_len;
break;
/*
case NS_Resource_RecordType:
case CNAME_Resource_RecordType:
case SOA_Resource_RecordType:
case PTR_Resource_RecordType:
case MX_Resource_RecordType:
case TXT_Resource_RecordType:
*/
default:
rte_free(rr);
msg->rcode = NotImplemented_ResponseType;
printf("Cannot answer question of type %d.\n", q->qType);
goto next;
}
msg->anCount++;
// prepend resource record to answers list
beg = msg->answers;
msg->answers = rr;
rr->next = beg;
// jump here to omit question
next:
// process next question
q = q->next;
}
}
/* @return 0 upon failure, 1 upon success */
int encode_resource_records(struct ResourceRecord *rr, uint8_t **buffer)
{
int i;
while (rr) {
// Answer questions by attaching resource sections.
encode_domain_name(buffer, rr->name);
put16bits(buffer, rr->type);
put16bits(buffer, rr->class);
put32bits(buffer, rr->ttl);
put16bits(buffer, rr->rd_length);
switch (rr->type) {
case A_Resource_RecordType:
for(i = 0; i < 4; ++i)
put8bits(buffer, rr->rd_data.a_record.addr[i]);
break;
case AAAA_Resource_RecordType:
for(i = 0; i < 16; ++i)
put8bits(buffer, rr->rd_data.aaaa_record.addr[i]);
break;
case TXT_Resource_RecordType:
put8bits(buffer, rr->rd_data.txt_record.txt_data_len);
for(i = 0; i < rr->rd_data.txt_record.txt_data_len; i++)
put8bits(buffer, rr->rd_data.txt_record.txt_data[i]);
break;
default:
fprintf(stderr, "Unknown type %u. => Ignore resource record.\n", rr->type);
return 1;
}
rr = rr->next;
}
return 0;
}
/* @return 0 upon failure, 1 upon success */
int encode_msg(struct Message *msg, uint8_t **buffer)
{
struct Question *q;
int rc;
encode_header(msg, buffer);
q = msg->questions;
while (q) {
encode_domain_name(buffer, q->qName);
put16bits(buffer, q->qType);
put16bits(buffer, q->qClass);
q = q->next;
}
rc = 0;
rc |= encode_resource_records(msg->answers, buffer);
rc |= encode_resource_records(msg->authorities, buffer);
rc |= encode_resource_records(msg->additionals, buffer);
return rc;
}
void free_resource_records(struct ResourceRecord *rr)
{
struct ResourceRecord *next;
while (rr) {
rte_free(rr->name);
next = rr->next;
rte_free(rr);
rr = next;
}
}
void free_questions(struct Question *qq)
{
struct Question *next;
while (qq) {
rte_free(qq->qName);
next = qq->next;
rte_free(qq);
qq = next;
}
}
再在我们之前实现的代码中进行修改,改一下udp的实现
if (UDP_PORT == ntohs(udp_hdr->dst_port)) {
#if ENABLE_DNS
g_src_ip = ip_hdr->dst_addr;
g_dest_ip = ip_hdr->src_addr;
g_src_port = ntohs(udp_hdr->dst_port);
g_dest_port = ntohs(udp_hdr->src_port);
rte_memcpy(g_dest_mac_addr, ehdr->s_addr.addr_bytes, RTE_ETHER_ADDR_LEN);
// udp userdata
uint16_t length = ntohs(udp_hdr->dgram_len);
uint16_t nbytes = length - sizeof(struct rte_udp_hdr);
uint8_t *data = (uint8_t*)(udp_hdr+1);
// decode_msg
free_questions(msg.questions);
free_resource_records(msg.answers);
free_resource_records(msg.authorities);
free_resource_records(msg.additionals);
memset(&msg, 0, sizeof(struct Message));
decode_msg(&msg, data, nbytes);
// resolve_query
resolve_query(&msg);
// encode_msg
uint8_t *p = data;
encode_msg(&msg, &p);
// send_udp_pkt
int len = p - data;
do_send_udp(pktmbuf_pool, data, len);
}
其实就四步,解析数据、处理数据、编码数据、回发。
编译完成后运行代码,注意运行之前设置kni回发,运行后执行命令ifconfig vEth0 192.168.0.120 hw 00:0c:29:85:2e:88 up
,然后就可以使用刚才介绍的dns测试工具进行测试了。