wenquan2015 opened a new pull request, #17711:
URL: https://github.com/apache/nuttx/pull/17711
## Summary
check tcp header ack seq is acceptable according rfc793
## Impact
tcp
## Testing
test1:syn-recved, receive unacceptable ack, send reset
```
from scapy.all import *
import time
targetip="10.0.1.2"
targetport=5000
pkt=IP(dst=targetip)/TCP(sport=12345,dport=targetport,seq=1526396415,flags="S")
ret=sr1(pkt)
time.sleep(0.1)
pkt=IP(dst=targetip)/TCP(sport=12345,dport=targetport,seq=ret.ack,
ack=ret.seq+6,flags="A")
send(pkt)
```
test1 result:
```
13:41:24.087735 IP 10.0.1.1.12345 > 10.0.1.2.5000: Flags [S], seq
1526396415, win 8192, length 0
13:41:24.096871 IP 10.0.1.2.5000 > 10.0.1.1.12345: Flags [S.], seq
1282192172, ack 1526396416, win 16384, options [mss 1460], length 0
13:41:24.217580 IP 10.0.1.1.12345 > 10.0.1.2.5000: Flags [.], ack 6, win
8192, length 0
13:41:24.226862 IP 10.0.1.2.5000 > 10.0.1.1.12345: Flags [R.], seq 6, ack 1,
win 0, length 0
```
test1: In finwait2, receive unacceptable ack, response an ack
```
from scapy.all import *
import time
targetip="10.0.1.2"
targetport=5000
pkt=IP(dst=targetip)/TCP(sport=12345,dport=targetport,seq=1287545596,
flags="S")
ret=sr1(pkt)
data_ack = IP(dst=targetip)/TCP(
sport=12345,
dport=targetport,
flags="A",
seq= ret.ack,
ack= ret.seq + 1
)
ret=sr1(data_ack)
finpkt=IP(dst=targetip)/TCP(sport=12345,dport=targetport,seq=ret.ack,
ack=ret.seq+1, flags="A")
send(finpkt)
errackpkt=IP(dst=targetip)/TCP(sport=12345,dport=targetport,seq=ret.ack,
ack=ret.seq+65535, flags="A")/"aaa"
send(errackpkt)
```
test2 result:
```
13:51:21.726043 IP 10.0.1.1.12345 > 10.0.1.2.5000: Flags [S], seq
1287545596, win 8192, length 0
13:51:21.735224 IP 10.0.1.2.5000 > 10.0.1.1.12345: Flags [S.], seq
1282192172, ack 1287545597, win 16384, options [mss 1460], length 0
13:51:21.758669 IP 10.0.1.1.12345 > 10.0.1.2.5000: Flags [.], ack 1, win
8192, length 0
13:51:31.775353 IP 10.0.1.2.5000 > 10.0.1.1.12345: Flags [F.], seq 1, ack 1,
win 16384, length 0
13:51:31.790697 IP 10.0.1.1.12345 > 10.0.1.2.5000: Flags [.], ack 2, win
8192, length 0
13:51:31.813148 IP 10.0.1.1.12345 > 10.0.1.2.5000: Flags [.], seq 1:4, ack
65536, win 8192, length 3
13:51:31.815022 IP 10.0.1.2.5000 > 10.0.1.1.12345: Flags [.], ack 1, win
16384, length 0
```
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