blocks|key|4595651|text|建立连接后，序列号会递增。理想情况下，新连接上的初始序列号是随机选择的，但许多操作系统都有一些半随机算法。RFC是发现更多TCP+RFC的最好地方。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4595652|entityMap|0|LINK|mutability|MUTABLE|url|http://www.faqs.org/rfcs/rfc793.html^0|1P|7|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

The sequence numbers increment after a connection is established. The initial sequence number on a new connection is ideally chosen at random but a lot of OS's have some semi-random algorithm. The RFC's are the best place to find out more <a href="http://www.faqs.org/rfcs/rfc793.html" rel="nofollow noreferrer">TCP RFC</a>.

blocks|key|530793|text|RFC+793+3.3节介绍了序列号。上次我在那个级别编写代码时，我想我们只是为持续存在的序列号保留了一个向上的计数器。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|530794|entityMap|0|LINK|mutability|MUTABLE|url|http://www.faqs.org/rfcs/rfc793.html^0|0|7|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

<a href="http://www.faqs.org/rfcs/rfc793.html" rel="nofollow noreferrer">RFC 793</a> section 3.3 covers sequence numbers. Last time I wrote code at that level, I think we just kept a one-up counter for sequence numbers that persisted.

blocks|key|4595762|text|这些值引用数据包的有效负载起始相对于连接的初始序列号的预期偏移量。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4595763|Reference|offset|length|4595764|4595765|序列号(32位)-具有双重作用，如果设置了SYN标志，则这是初始序列号。实际第一个数据字节的序列号将是该序列号加1。如果未设置SYN标志，则这是第一个数据字节的序列号|blockquote|4595766|4595767|确认号(32位)-如果设置了确认标志，则此字段的值是接收方期望的下一个预期字节。|4595768|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Transmission_Control_Protocol^0|0|0|9|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@$D|W|E|X|1|Y]]|A|$]]|$1|F|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|G|3|H|5|I|7|10|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|11|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|12|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|13|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

These values reference the expected offsets of the start of the payload for the packet relative to the initial sequence number for the connection.

<a href="http://en.wikipedia.org/wiki/Transmission_Control_Protocol" rel="nofollow noreferrer">Reference</a>

<blockquote>
 Sequence number (32 bits) – has a dual
 role If the SYN flag is set, then this
 is the initial sequence number. The
 sequence number of the actual first
 data byte will then be this sequence
 number plus 1. If the SYN flag is not
 set, then this is the sequence number
 of the first data byte
 
 Acknowledgement
 number (32 bits) – if the ACK flag is
 set then the value of this field is
 the next expected byte that the
 receiver is expecting.
</blockquote>

blocks|key|530873|text|两端随机生成数字，然后增加发送的二进制八位数(字节)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|530874|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Numbers are randomly generated from both sides, then increased by number of octets (bytes) send.

blocks|key|1126441|text|建立TCP连接时，每一端都会生成一个随机数作为其初始序列号。它是一个强随机数:如果互联网上的任何人都能猜到序列号，那么就存在安全问题，因为他们可以很容易地伪造数据包注入到TCP流中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1126442|此后，对于传输的每个字节，序列号将递增1。ACK字段是来自另一端的序列号，被发回以确认接收。|1126443|原始的TCP协议规范RFC+793可以提供很大的帮助。|offset|length|1126444|entityMap|0|LINK|mutability|MUTABLE|url|https://www.rfc-editor.org/rfc/rfc793^0|0|0|A|7|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Q|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@$F|S|G|T|1|U]]|A|$]]|$1|H|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|O]]]]

When a TCP connection is established, each side generates a random number as its initial sequence number. It is a strongly random number: there are security problems if anybody on the internet can guess the sequence number, as they can easily forge packets to inject into the TCP stream.
Thereafter, for every byte transmitted the sequence number will increment by 1. The ACK field is the sequence number from the other side, sent back to acknowledge reception.
<a href="https://www.rfc-editor.org/rfc/rfc793" rel="nofollow noreferrer">RFC 793</a>, the original TCP protocol specification, can be of great help.

blocks|key|1131488|text|似乎其余的答案几乎都解释了在哪里可以找到关于ACK的详细和官方信息，即TCP+RFC|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1131489|下面是我在执行类似实现时发现的一个更实用、更“容易理解”的页面，它也可能对TCP+Analysis+-+Section+2:+Sequence+&+Acknowledgement+Numbers有所帮助|1131490|entityMap|0|LINK|mutability|MUTABLE|url|https://www.rfc-editor.org/rfc/rfc793|1|http://www.firewall.cx/tcp-analysis-section-2.php^0|Z|7|0|0|11|1O|1|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]]|C|$]]|$1|F|3|-4|5|6|7|X|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|O]]]]

Seems that the rest of the answers explained pretty much all about where to find detailed and official information about ACK's, namely <a href="https://www.rfc-editor.org/rfc/rfc793" rel="nofollow noreferrer">TCP RFC</a>
Here's a more practical and &quot;easy understood&quot; page that I found when I was doing similar implementations that may also help <a href="http://www.firewall.cx/tcp-analysis-section-2.php" rel="nofollow noreferrer">TCP Analysis - Section 2: Sequence &amp; Acknowledgement Numbers</a>

blocks|key|530979|text|如果我理解正确的话，您正在尝试挂载TCP+SEQ+prediction+attack。如果是这样的话，您将需要研究目标操作系统的Initial+Sequence+Number生成器的细节。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|530980|在相当多的all+the+major+OS's+wrt中有广泛宣传的漏洞，它们的ISN生成器是可预测的。我没有密切关注它的后果，但我的理解是，大多数供应商都发布了randomize+their+ISN+increments的补丁。|530981|entityMap|0|LINK|mutability|MUTABLE|url|http://www.tech-faq.com/tcp-sequence-prediction.shtml|1|http://www.ietf.org/rfc/rfc1948.txt|2|http://lcamtuf.coredump.cx/newtcp/|3|http://msdn.microsoft.com/en-us/library/ms819768.aspx^0|H|P|0|1S|N|1|0|5|I|2|29|U|3|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]|$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|E|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]|$A|14|B|15|1|16]]|C|$]]|$1|F|3|-4|5|6|7|17|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|O]]|P|$5|I|J|K|C|$L|Q]]|R|$5|I|J|K|C|$L|S]]]]

If I understand you correctly - you're trying to mount a <a href="http://www.tech-faq.com/tcp-sequence-prediction.shtml" rel="noreferrer">TCP SEQ prediction attack</a>. If that's the case, you'll want to study the specifics of your target OS's <a href="http://www.ietf.org/rfc/rfc1948.txt" rel="noreferrer">Initial Sequence Number</a> generator.

There were widely publicized vulnerabilties in pretty much <a href="http://lcamtuf.coredump.cx/newtcp/" rel="noreferrer">all the major OS's</a> wrt their ISN generators being predictable. I haven't followed the fallout closely, but my understanding is that most vendors released patches to <a href="http://msdn.microsoft.com/en-us/library/ms819768.aspx" rel="noreferrer">randomize their ISN increments</a>.

blocks|key|3751185|text|我也有同样的工作要做。首先，随机生成初始seq#+(0-4294967297)。然后接收方对接收到的数据长度进行计数，并将seq#+%2B+length+=+x的确认信息发送给发送方。然后，序列将是x，发送者将发送数据。类似地，接收器将计算长度ACK，并将x+%2B+length+=+y作为y发送，以此类推……它是如何生成seq/ack的.|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3751186|如果你想实际地展示它，尝试在Wireshark中嗅探数据包，然后跟踪TCP流并查看场景……|3751187|entityMap^0|1P|H|3I|E|3Y|1|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|R|8|@]|D|@]|E|$]]]|I|$]]

I have the same job to do.
Firstly the initial seq# will be generated randomly(0-4294967297).
Then the receiver will count the length of the data it received and send the ACK of <code>seq# + length = x</code> to the sender. The sequence will then be x and the sender will send the data. Similarly the receiver will count the length <code>x + length = y</code> and send the ACK as <code>y</code> and so on... Its how the the seq/ack is generated...

If you want to show it practically try to sniff a packet in Wireshark and follow the TCP stream and see the scenario...

I am currently working on a program which sniffs TCP packets being sent and received to and from a particular address. What I am trying to accomplish is replying with custom tailored packets to certain received packets. I've already got the parsing done. I can already generated valid Ethernet, IP, and--for the most part--TCP packets.

The only thing that I cannot figure out is how the seq / ack numbers are determined.

While this may be irrelevant to the problem, the program is written in C++ using WinPCap. I am asking for any tips, articles, or other resources that may help me.

TCP: How are the seq / ack numbers generated?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我目前正在开发一个程序，该程序可以嗅探发送到特定地址和从特定地址接收的TCP数据包。我试图完成的是用定制的数据包回复某些接收到的数据包。我已经完成了解析。我已经可以生成有效的以太网、IP和TCP数据包。我唯一不能理解的是seq / ack数字是如何确定的。虽然这可能与问题无关，但该程序是使用WinPCap用C++编写的...

问TCP:序列号/确认号是如何生成的？
EN

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问TCP:序列号/确认号是如何生成的？EN