Based on the previously implemented KNI Code , And combine dns Open source library code dpdk-dns The combination of

Reference link ：https://blog.csdn.net/yun6853992/article/details/122150555

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One 、DNS The domain name system

1.DNS effect

DNS（Domain Name System Abbreviation ） It's very simple . Will domain name and ip Mutual mapping , Generally used for domain name resolution , It's based on the domain name IP Address .

• DNS Use udp port 53;
• The hierarchy of domain names ： Domain name by “.” division ,eg： Host name . Subdomains . Top-level domain name . Root domain name , the last one “.” Omit , By default, it is managed by the root ;
• Hierarchical query ： Enter a web address （ domain name ）, First, it looks for the browser cache , then DNS The server is based on the hierarchy of domain names , Hierarchical query .dig Ordered +trace Parameters can show DNS The whole hierarchical query process of .
• DNS The type of record ：dns Somewhat type type , To determine the dns Message processing , Such as A Record 、AAAA Record 、CNAME Record 、MX Record 、NS Record 、TXT Record 、SRV Record 、URL forward .

2. Lookup process

Although you only need to return one IP Address , however DNS The query process is very complicated , It's divided into multiple steps .
Tool software dig The whole query process can be displayed .

root@ubuntu:~# dig www.baidu.com

#  The first part ： Query parameters and statistics 
; <<>> DiG 9.10.3-P4-Ubuntu <<>> www.baidu.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 5575
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1

#  The second part ： Query content 
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;www.baidu.com.			IN	A

#  The third part ：DNS The server's reply 
#  Show www.baidu.com. There is one CNAME Record , as well as www.a.shifen.com. There are two A Record 
# 415、146 yes TTL value , Indicates the cache time , namely 415s There is no need to re query 
;; 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

#  The fourth part ：DNS Some transmission information of the server 
#  Results show , This machine DNS Server is 192.168.2.1, The query port is 53（DNS Server default port ）, The response length is 101 byte 
;; Query time: 2 msec
;; SERVER: 192.168.2.1#53(192.168.2.1)
;; WHEN: Sat Apr 16 01:39:18 PDT 2022
;; MSG SIZE  rcvd: 104

If you don't want to see so much , You can use +short Parameters

root@ubuntu:~# dig www.baidu.com +short
www.a.shifen.com.
14.215.177.39
14.215.177.38

The above command only returns www.baidu.com Corresponding 2 individual IP Address （ namely A Record ）.

This machine only to its own DNS Server query ,dig The order has a @ Parameters , Show to other DNS The result of the server query .

$ dig @4.2.2.2 www.baidu.com

The command above refers to orientation DNS The server 4.2.2.2 Inquire about .

3. other DNS Tools

（1）host command

host The command can be seen as dig A simplified version of the command , Return all kinds of records of the current request domain name .

$ host github.com

github.com has address 192.30.252.121
github.com mail is handled by 5 ALT2.ASPMX.L.GOOGLE.COM.
github.com mail is handled by 10 ALT4.ASPMX.L.GOOGLE.COM.
github.com mail is handled by 10 ALT3.ASPMX.L.GOOGLE.COM.
github.com mail is handled by 5 ALT1.ASPMX.L.GOOGLE.COM.
github.com mail is handled by 1 ASPMX.L.GOOGLE.COM.


$ host facebook.github.com

facebook.github.com is an alias for github.map.fastly.net.
github.map.fastly.net has address 103.245.222.133

host Commands can also be used for reverse queries , From IP Address query domain name , Equate to dig -x .

$ host 192.30.252.153

153.252.30.192.in-addr.arpa domain name pointer pages.github.com.

（2）nslookup command

nslookup The command is used to query domain name records interactively .

root@ubuntu:~# nslookup www.baidu.com
Server:		192.168.2.1
Address:	192.168.2.1#53

Non-authoritative answer:
www.baidu.com	canonical name = www.a.shifen.com.
Name:	www.a.shifen.com
Address: 14.215.177.39
Name:	www.a.shifen.com
Address: 14.215.177.38

Learn how to resolve from the root domain name ip The process of

root@ubuntu:~$ nslookup
> set type=ns    # Set the domain name resolution server record   To view the 
> .				 # View the root domain service record 
Server:		192.168.0.1
Address:	192.168.0.1#53

Non-authoritative answer:   # Intermediate cache   Not authoritative 
.	nameserver = m.root-servers.net.
.	nameserver = a.root-servers.net.
.	nameserver = l.root-servers.net.
.	nameserver = c.root-servers.net.
.	nameserver = d.root-servers.net.
.	nameserver = k.root-servers.net.
.	nameserver = j.root-servers.net.
.	nameserver = e.root-servers.net.
.	nameserver = g.root-servers.net.
.	nameserver = f.root-servers.net.
.	nameserver = b.root-servers.net.
.	nameserver = i.root-servers.net.
.	nameserver = h.root-servers.net.

Authoritative answers can be found from:
a.root-servers.net	internet address = 198.41.0.4
b.root-servers.net	internet address = 199.9.14.201
c.root-servers.net	internet address = 192.33.4.12
d.root-servers.net	internet address = 199.7.91.13
e.root-servers.net	internet address = 192.203.230.10
f.root-servers.net	internet address = 192.5.5.241
g.root-servers.net	internet address = 192.112.36.4
h.root-servers.net	internet address = 198.97.190.53
i.root-servers.net	internet address = 192.36.148.17
j.root-servers.net	internet address = 192.58.128.30
k.root-servers.net	internet address = 193.0.14.129
l.root-servers.net	internet address = 199.7.83.42
m.root-servers.net	internet address = 202.12.27.33
a.root-servers.net	has AAAA address 2001:503:ba3e::2:30
b.root-servers.net	has AAAA address 2001:500:200::b

> set type=a		# Set type to a  lookup ip
> a.root-servers.net.	# View one of the domain name nodes ip
Server:		192.168.0.1
Address:	192.168.0.1#53

Non-authoritative answer:
Name:	a.root-servers.net
Address: 198.41.0.4

> server 198.41.0.4   # Set up domain name server 
Default server: 198.41.0.4
Address: 198.41.0.4#53

> set type=ns		# View the root domain name server 
> com.				# Request... Under the root domain name server , Check and you will find that you will only go to what we set up server Conduct 
Server:		198.41.0.4
Address:	198.41.0.4#53

Non-authoritative answer:
*** Cant find com.: No answer

Authoritative answers can be found from:
com	nameserver = a.gtld-servers.net.
com	nameserver = b.gtld-servers.net.
com	nameserver = c.gtld-servers.net.
com	nameserver = d.gtld-servers.net.
com	nameserver = e.gtld-servers.net.
com	nameserver = f.gtld-servers.net.
com	nameserver = g.gtld-servers.net.
com	nameserver = h.gtld-servers.net.
com	nameserver = i.gtld-servers.net.
com	nameserver = j.gtld-servers.net.
com	nameserver = k.gtld-servers.net.
com	nameserver = l.gtld-servers.net.
com	nameserver = m.gtld-servers.net.
a.gtld-servers.net	internet address = 192.5.6.30
b.gtld-servers.net	internet address = 192.33.14.30
c.gtld-servers.net	internet address = 192.26.92.30
d.gtld-servers.net	internet address = 192.31.80.30
e.gtld-servers.net	internet address = 192.12.94.30
f.gtld-servers.net	internet address = 192.35.51.30
g.gtld-servers.net	internet address = 192.42.93.30
h.gtld-servers.net	internet address = 192.54.112.30
i.gtld-servers.net	internet address = 192.43.172.30
j.gtld-servers.net	internet address = 192.48.79.30
k.gtld-servers.net	internet address = 192.52.178.30
l.gtld-servers.net	internet address = 192.41.162.30
m.gtld-servers.net	internet address = 192.55.83.30
a.gtld-servers.net	has AAAA address 2001:503:a83e::2:30
b.gtld-servers.net	has AAAA address 2001:503:231d::2:30
> server 192.5.6.30
Default server: 192.5.6.30
Address: 192.5.6.30#53

> set type=ns				# Test an actual domain name 
> bilibili.com
Server:		192.5.6.30
Address:	192.5.6.30#53

Non-authoritative answer:
*** Can't find bilibili.com: No answer

Authoritative answers can be found from:
bilibili.com	nameserver = ns3.dnsv5.com.
bilibili.com	nameserver = ns4.dnsv5.com.
ns3.dnsv5.com	internet address = 129.211.176.212
ns3.dnsv5.com	internet address = 162.14.18.188
ns3.dnsv5.com	internet address = 162.14.24.251
ns3.dnsv5.com	internet address = 162.14.25.251
ns3.dnsv5.com	internet address = 18.194.2.137
ns3.dnsv5.com	internet address = 183.192.201.94
ns3.dnsv5.com	internet address = 223.166.151.16
ns3.dnsv5.com	has AAAA address 2402:4e00:1430:1102:0:9136:2b2b:ba61
ns3.dnsv5.com	internet address = 52.77.238.92
ns3.dnsv5.com	internet address = 61.151.180.51
ns4.dnsv5.com	internet address = 101.226.220.12
ns4.dnsv5.com	internet address = 129.211.176.151
ns4.dnsv5.com	internet address = 162.14.24.248
ns4.dnsv5.com	internet address = 162.14.25.248
ns4.dnsv5.com	internet address = 183.192.164.119
ns4.dnsv5.com	internet address = 223.166.151.126
ns4.dnsv5.com	has AAAA address 2402:4e00:1020:1264:0:9136:29b6:fc32
ns4.dnsv5.com	internet address = 52.198.159.146
ns4.dnsv5.com	internet address = 59.36.120.147

> server 129.211.176.212			# Set up com Corresponding top-level domain name server 
Default server: 129.211.176.212
Address: 129.211.176.212#53
> set type=a					# Set type to a, Find corresponding ip
> www.bilibili.com.      		# see ip, Find the corresponding content distribution domain name 
Server:		129.211.176.212
Address:	129.211.176.212#53

www.bilibili.com	canonical name = b.w.bilicdn1.com.
> b.w.bilicdn1.com.				# View the corresponding content distribution domain name ip, That's what we need ip 
Server:		129.211.176.212
Address:	129.211.176.212#53

Name:	b.w.bilicdn1.com
Address: 119.3.211.130
Name:	b.w.bilicdn1.com
Address: 119.3.231.166
Name:	b.w.bilicdn1.com
Address: 119.3.238.64
Name:	b.w.bilicdn1.com
Address: 119.3.229.89
Name:	b.w.bilicdn1.com
Address: 119.3.234.165
Name:	b.w.bilicdn1.com
Address: 119.3.227.169

What we got here ip Will be returned to our local dns Server and cache , When sending to our browser to enter the domain name , The corresponding procedure , use ip Make an actual request .

（3）whois command

whois The command is used to check the registration of domain names .

$ whois github.com

Two 、DNS Realization

dns Is based on udp Realized .

1. Realize the idea

Reference resources udp Protocol header and dns The head of the agreement , Construct the corresponding head structure , Yes DNS The server makes a data request , You should be able to get the returned ip.

receive（ receive udp package ）
===> decode_msg（ Parsing packets ）
===> resolve_query（ Look up the table ）
===> encode_msg（ pack ）
===> send（ Send back packet ）

2. Test ideas

• Use it directly udp socket api Make a data request , Structural compliance dns The structure data of the protocol can ;
• Parse the received udp Reply message data . Get what you need ip that will do .

3、 ... and 、 Two open source DNS Realization

1.dnspod-sr

# Compile and run 
root@ubuntu:/root/dnspod-sr-master/src# ./dnspod-sr 
[DBG:] dnspod-sr is successfully running now!!
[DBG:] max_ele_size is 1000000 - 1808
[DBG:] server may contain 332730 useful records
[DBG:] hash_table_size is 65536
[DBG:] we have 10 hash tables
[DBG:] we have 2 fetchers,2 quizzers

Use... In another environment dig Command to test ,dns The server has the function of learning

root@ubuntu:/home/root# dig @192.168.105.143 www.bilibili.com

; <<>> DiG 9.10.3-P4-Ubuntu <<>> @192.168.105.143 www.bilibili.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 8662
;; flags: qr ra; QUERY: 1, ANSWER: 8, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;www.bilibili.com.		IN	A

;; ANSWER SECTION:
www.bilibili.com.	214	IN	CNAME	b.w.bilicdn1.com.
b.w.bilicdn1.com.	104	IN	A	120.92.113.99
b.w.bilicdn1.com.	104	IN	A	120.92.108.182
b.w.bilicdn1.com.	104	IN	A	120.92.83.126
b.w.bilicdn1.com.	104	IN	A	120.92.82.179
b.w.bilicdn1.com.	104	IN	A	120.92.211.159
b.w.bilicdn1.com.	104	IN	A	120.131.2.207
b.w.bilicdn1.com.	104	IN	A	120.92.78.97

;; Query time: 2951 msec
;; SERVER: 192.168.105.143#53(192.168.105.143)
;; WHEN: Sat Dec 25 16:50:18 CST 2021
;; MSG SIZE  rcvd: 173

Use dnsperf Test performance ：

# install dnsperf https://gitee.com/mirrors_DNS-OARC/dnsperf?_from=gitee_search
# Pay attention to the first way   Installation of version package , I reported an error when installing with the source code 
# Installation package download address https://www.dns-oarc.net/tools/dnsperf
tar -xvf dnsperf-2.9.0.tar.gz 
cd dnsperf-2.9.0
./configure 
make
make install

# Write a configuration file   as follows  
root@ubuntu:/root/dnsperf-2.9.0# cat testfile 
www.baidu.com A
www.bilibili.com A
# Perform the test , Can analyze the results 
./src/dnsperf -d testfile -s 192.168.105.143 -c10000 -q10000 -l60

2.simpleDNS

download ：https://github.com/mwarning/SimpleDNS.git

Start the code executable , use dig Request to view ：

#dig @192.168.105.143 -p 9000 foo.bar.com A
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 8362
;; flags: qr; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;foo.bar.com.			IN	A

;; ANSWER SECTION:
foo.bar.com.		3600	IN	A	192.168.1.1  # This is the domain name written in the test code （foo.bar.com） Corresponding ip

;; Query time: 0 msec
;; SERVER: 192.168.105.143#9000(192.168.105.143)
;; WHEN: Sat Dec 25 22:07:24 CST 2021
;; MSG SIZE  rcvd: 56

Four 、dpdk-dns

1. Ideas

• Use dpdk Provided interface , To take over udp The data of , Yes dns Relevant requests are processed by agreement ;
• Reference resources simpleDNS Logic , Existing dpdk Handle arp,udp, tcp Based on the logic of , increase udp When the message ,dns Processing of relevant data ;
• Reference resources simpleDNS The logic in the is used for business processing and returns .

2. Turn on KNI Postback

kni Be able to carry on tx Send the data back to the kernel for processing , But you can't get the data looped back from the kernel , namely kni Conduct rx But I can't receive data . At this time, loop back processing is required ：
Method 1 ： Go to “/sys/devices/virtual/net/%s/carrier” Write in 1, Open the loop .
Method 2 ： Insert KNI Module time , take carrier Set to on

root@ubuntu:~/share# cd dpdk/
root@ubuntu:~/share/dpdk# cd x86_64-native-linux-gcc/kmod/
root@ubuntu:~/share/dpdk/x86_64-native-linux-gcc/kmod# ls
igb_uio.ko  rte_kni.ko
root@ubuntu:~/share/dpdk/x86_64-native-linux-gcc/kmod# insmod rte_kni.ko carrier=on

Method 3 ： Call in code rte_kni_update_link, Dynamically enable the function of sending back data .

3.dns Data processing

if (UDP_PORT == ntohs(udp_hdr->dest_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);