As you can see here, the Python code handles a specific case of Oracle TNS layer requesting a RESEND of the last packet. I’ve noticed that no matter what client I’m trying to connect with, Oracle is always requesting a RESEND after the initial CONNECT request as you can see here (removed various ACK packets, etc.):
1. Using SQL*Plus
Packet number 13:
From: 127.0.0.1
To: 127.0.0.1
Protocol: TCP
Src port: 63055
Dst port: 1521
Packet Type: Connect
Version: 01 3a
SDU/TDU: 8192 / 32512
SERVICE_NAME: db11200
SID: <N/A>
HOST: slavik-laptop
PROGRAM: sqlplus
USER: slavik
Payload (216 bytes):
00000 00 d8 00 00 01 00 00 00 01 3a 01 2c 0c 41 20 00 .........:.,.A .
00016 7f ff 7f 08 00 00 01 00 00 9e 00 3a 00 00 08 00 ...........:....
00032 41 41 00 00 00 00 00 00 00 00 00 00 00 00 00 00 AA..............
00048 00 00 00 00 00 00 00 00 00 00 28 44 45 53 43 52 ..........(DESCR
00064 49 50 54 49 4f 4e 3d 28 43 4f 4e 4e 45 43 54 5f IPTION=(CONNECT_
00080 44 41 54 41 3d 28 53 45 52 56 49 43 45 5f 4e 41 DATA=(SERVICE_NA
00096 4d 45 3d 64 62 31 31 32 30 30 29 28 43 49 44 3d ME=db11200)(CID=
00112 28 50 52 4f 47 52 41 4d 3d 73 71 6c 70 6c 75 73 (PROGRAM=sqlplus
00128 29 28 48 4f 53 54 3d 73 6c 61 76 69 6b 2d 6c 61 )(HOST=slavik-la
00144 70 74 6f 70 29 28 55 53 45 52 3d 73 6c 61 76 69 ptop)(USER=slavi
00160 6b 29 29 29 28 41 44 44 52 45 53 53 3d 28 50 52 k)))(ADDRESS=(PR
00176 4f 54 4f 43 4f 4c 3d 54 43 50 29 28 48 4f 53 54 OTOCOL=TCP)(HOST
00192 3d 31 32 37 2e 30 2e 30 2e 31 29 28 50 4f 52 54 =127.0.0.1)(PORT
00208 3d 31 35 32 31 29 29 29 =1521)))
Packet number 15:
From: 127.0.0.1
To: 127.0.0.1
Protocol: TCP
Src port: 1521
Dst port: 63055
Packet Type: Resend
Payload (8 bytes):
00000 00 08 00 00 0b 00 00 00 ........
Packet number 17:
From: 127.0.0.1
To: 127.0.0.1
Protocol: TCP
Src port: 63055
Dst port: 1521
Packet Type: Connect
Version: 01 3a
SDU/TDU: 8192 / 32512
SERVICE_NAME: db11200
SID: <N/A>
HOST: slavik-laptop
PROGRAM: sqlplus
USER: slavik
Payload (216 bytes):
00000 00 d8 00 00 01 00 00 00 01 3a 01 2c 0c 41 20 00 .........:.,.A .
00016 7f ff 7f 08 00 00 01 00 00 9e 00 3a 00 00 08 00 ...........:....
00032 41 41 00 00 00 00 00 00 00 00 00 00 00 00 00 00 AA..............
00048 00 00 00 00 00 00 00 00 00 00 28 44 45 53 43 52 ..........(DESCR
00064 49 50 54 49 4f 4e 3d 28 43 4f 4e 4e 45 43 54 5f IPTION=(CONNECT_
00080 44 41 54 41 3d 28 53 45 52 56 49 43 45 5f 4e 41 DATA=(SERVICE_NA
00096 4d 45 3d 64 62 31 31 32 30 30 29 28 43 49 44 3d ME=db11200)(CID=
00112 28 50 52 4f 47 52 41 4d 3d 73 71 6c 70 6c 75 73 (PROGRAM=sqlplus
00128 29 28 48 4f 53 54 3d 73 6c 61 76 69 6b 2d 6c 61 )(HOST=slavik-la
00144 70 74 6f 70 29 28 55 53 45 52 3d 73 6c 61 76 69 ptop)(USER=slavi
00160 6b 29 29 29 28 41 44 44 52 45 53 53 3d 28 50 52 k)))(ADDRESS=(PR
00176 4f 54 4f 43 4f 4c 3d 54 43 50 29 28 48 4f 53 54 OTOCOL=TCP)(HOST
00192 3d 31 32 37 2e 30 2e 30 2e 31 29 28 50 4f 52 54 =127.0.0.1)(PORT
00208 3d 31 35 32 31 29 29 29 =1521)))
Packet number 19:
From: 127.0.0.1
To: 127.0.0.1
Protocol: TCP
Src port: 1521
Dst port: 63055
Packet Type: Accept
Accepted: Yes
Payload (32 bytes):
00000 00 20 00 00 02 00 00 00 01 3a 0c 41 20 00 7f ff . .......:.A ...
00016 01 00 00 00 00 20 41 41 00 00 00 00 00 00 00 00 ..... AA........
2. Using JDBC Type 4
Packet number 4:
From: 127.0.0.1
To: 127.0.0.1
Protocol: TCP
Src port: 49699
Dst port: 1521
Packet Type: Connect
Version: 01 36
SDU/TDU: 8192 / 32512
SERVICE_NAME: <N/A>
SID: db11200
HOST: __jdbc__
PROGRAM: JDBC Thin Client
USER: slavik
Payload (211 bytes):
00000 00 d3 00 00 01 00 00 00 01 36 01 2c 0e 41 20 00 .........6.,.A .
00016 7f ff 4f 98 00 00 00 01 00 99 00 3a 00 00 00 00 ..O........:....
00032 01 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00048 00 00 00 00 00 00 00 00 00 00 28 44 45 53 43 52 ..........(DESCR
00064 49 50 54 49 4f 4e 3d 28 43 4f 4e 4e 45 43 54 5f IPTION=(CONNECT_
00080 44 41 54 41 3d 28 53 49 44 3d 64 62 31 31 32 30 DATA=(SID=db1120
00096 30 29 28 43 49 44 3d 28 50 52 4f 47 52 41 4d 3d 0)(CID=(PROGRAM=
00112 4a 44 42 43 20 54 68 69 6e 20 43 6c 69 65 6e 74 JDBC Thin Client
00128 29 28 48 4f 53 54 3d 5f 5f 6a 64 62 63 5f 5f 29 )(HOST=__jdbc__)
00144 28 55 53 45 52 3d 73 6c 61 76 69 6b 29 29 29 28 (USER=slavik)))(
00160 41 44 44 52 45 53 53 3d 28 50 52 4f 54 4f 43 4f ADDRESS=(PROTOCO
00176 4c 3d 74 63 70 29 28 48 4f 53 54 3d 6c 6f 63 61 L=tcp)(HOST=loca
00192 6c 68 6f 73 74 29 28 50 4f 52 54 3d 31 35 32 31 lhost)(PORT=1521
00208 29 29 29 )))
Packet number 6:
From: 127.0.0.1
To: 127.0.0.1
Protocol: TCP
Src port: 1521
Dst port: 49699
Packet Type: Resend
Payload (8 bytes):
00000 00 08 00 00 0b 00 00 00 ........
Packet number 8:
From: 127.0.0.1
To: 127.0.0.1
Protocol: TCP
Src port: 49699
Dst port: 1521
Packet Type: Connect
Version: 01 36
SDU/TDU: 8192 / 32512
SERVICE_NAME: <N/A>
SID: db11200
HOST: __jdbc__
PROGRAM: JDBC Thin Client
USER: slavik
Payload (211 bytes):
00000 00 d3 00 00 01 00 00 00 01 36 01 2c 0e 41 20 00 .........6.,.A .
00016 7f ff 4f 98 00 00 00 01 00 99 00 3a 00 00 00 00 ..O........:....
00032 01 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00048 00 00 00 00 00 00 00 00 00 00 28 44 45 53 43 52 ..........(DESCR
00064 49 50 54 49 4f 4e 3d 28 43 4f 4e 4e 45 43 54 5f IPTION=(CONNECT_
00080 44 41 54 41 3d 28 53 49 44 3d 64 62 31 31 32 30 DATA=(SID=db1120
00096 30 29 28 43 49 44 3d 28 50 52 4f 47 52 41 4d 3d 0)(CID=(PROGRAM=
00112 4a 44 42 43 20 54 68 69 6e 20 43 6c 69 65 6e 74 JDBC Thin Client
00128 29 28 48 4f 53 54 3d 5f 5f 6a 64 62 63 5f 5f 29 )(HOST=__jdbc__)
00144 28 55 53 45 52 3d 73 6c 61 76 69 6b 29 29 29 28 (USER=slavik)))(
00160 41 44 44 52 45 53 53 3d 28 50 52 4f 54 4f 43 4f ADDRESS=(PROTOCO
00176 4c 3d 74 63 70 29 28 48 4f 53 54 3d 6c 6f 63 61 L=tcp)(HOST=loca
00192 6c 68 6f 73 74 29 28 50 4f 52 54 3d 31 35 32 31 lhost)(PORT=1521
00208 29 29 29 )))
Packet number 10:
From: 127.0.0.1
To: 127.0.0.1
Protocol: TCP
Src port: 1521
Dst port: 49699
Packet Type: Accept
Accepted: Yes
Payload (32 bytes):
00000 00 20 00 00 02 00 00 00 01 36 0e 41 20 00 7f ff . .......6.A ...
00016 01 00 00 00 00 20 41 01 00 00 00 00 00 00 00 00 ..... A.........
3. Using an OCI with 10g client
Packet number 4:
From: 127.0.0.1
To: 127.0.0.1
Protocol: TCP
Src port: 40196
Dst port: 1521
Packet Type: Connect
Version: 01 39
SDU/TDU: 2048 / 32512
SERVICE_NAME: db11200
SID: <N/A>
HOST: slavik-laptop
PROGRAM: ocitest
USER: slavik
Payload (216 bytes):
00000 00 d8 00 00 01 00 00 00 01 39 01 2c 0c 01 08 00 .........9.,....
00016 7f ff 7f 08 00 00 01 00 00 9e 00 3a 00 00 02 00 ...........:....
00032 41 41 00 00 00 00 00 00 00 00 00 00 00 00 00 00 AA..............
00048 00 00 00 00 00 00 00 00 00 00 28 44 45 53 43 52 ..........(DESCR
00064 49 50 54 49 4f 4e 3d 28 43 4f 4e 4e 45 43 54 5f IPTION=(CONNECT_
00080 44 41 54 41 3d 28 53 45 52 56 49 43 45 5f 4e 41 DATA=(SERVICE_NA
00096 4d 45 3d 64 62 31 31 32 30 30 29 28 43 49 44 3d ME=db11200)(CID=
00112 28 50 52 4f 47 52 41 4d 3d 6f 63 69 74 65 73 74 (PROGRAM=ocitest
00128 29 28 48 4f 53 54 3d 73 6c 61 76 69 6b 2d 6c 61 )(HOST=slavik-la
00144 70 74 6f 70 29 28 55 53 45 52 3d 73 6c 61 76 69 ptop)(USER=slavi
00160 6b 29 29 29 28 41 44 44 52 45 53 53 3d 28 50 52 k)))(ADDRESS=(PR
00176 4f 54 4f 43 4f 4c 3d 54 43 50 29 28 48 4f 53 54 OTOCOL=TCP)(HOST
00192 3d 31 32 37 2e 30 2e 30 2e 31 29 28 50 4f 52 54 =127.0.0.1)(PORT
00208 3d 31 35 32 31 29 29 29 =1521)))
Packet number 6:
From: 127.0.0.1
To: 127.0.0.1
Protocol: TCP
Src port: 1521
Dst port: 40196
Packet Type: Resend
Payload (8 bytes):
00000 00 08 00 00 0b 00 00 00 ........
Packet number 8:
From: 127.0.0.1
To: 127.0.0.1
Protocol: TCP
Src port: 40196
Dst port: 1521
Packet Type: Connect
Version: 01 39
SDU/TDU: 2048 / 32512
SERVICE_NAME: db11200
SID: <N/A>
HOST: slavik-laptop
PROGRAM: ocitest
USER: slavik
Payload (216 bytes):
00000 00 d8 00 00 01 00 00 00 01 39 01 2c 0c 01 08 00 .........9.,....
00016 7f ff 7f 08 00 00 01 00 00 9e 00 3a 00 00 02 00 ...........:....
00032 41 41 00 00 00 00 00 00 00 00 00 00 00 00 00 00 AA..............
00048 00 00 00 00 00 00 00 00 00 00 28 44 45 53 43 52 ..........(DESCR
00064 49 50 54 49 4f 4e 3d 28 43 4f 4e 4e 45 43 54 5f IPTION=(CONNECT_
00080 44 41 54 41 3d 28 53 45 52 56 49 43 45 5f 4e 41 DATA=(SERVICE_NA
00096 4d 45 3d 64 62 31 31 32 30 30 29 28 43 49 44 3d ME=db11200)(CID=
00112 28 50 52 4f 47 52 41 4d 3d 6f 63 69 74 65 73 74 (PROGRAM=ocitest
00128 29 28 48 4f 53 54 3d 73 6c 61 76 69 6b 2d 6c 61 )(HOST=slavik-la
00144 70 74 6f 70 29 28 55 53 45 52 3d 73 6c 61 76 69 ptop)(USER=slavi
00160 6b 29 29 29 28 41 44 44 52 45 53 53 3d 28 50 52 k)))(ADDRESS=(PR
00176 4f 54 4f 43 4f 4c 3d 54 43 50 29 28 48 4f 53 54 OTOCOL=TCP)(HOST
00192 3d 31 32 37 2e 30 2e 30 2e 31 29 28 50 4f 52 54 =127.0.0.1)(PORT
00208 3d 31 35 32 31 29 29 29 =1521)))
Packet number 10:
From: 127.0.0.1
To: 127.0.0.1
Protocol: TCP
Src port: 1521
Dst port: 40196
Packet Type: Accept
Accepted: Yes
Payload (32 bytes):
00000 00 20 00 00 02 00 00 00 01 39 0c 01 08 00 7f ff . .......9......
00016 01 00 00 00 00 20 41 41 00 00 00 00 00 00 00 00 ..... AA........
This is using an Oracle server 11gR2 (11.2.0.1) 64bit.
So, my question is – why? Is this a clumsy attempt to thwart discovery tools? Some sort of a defense mechanism?
I would appreciate any insights here. I’m sure that there are knowledgeable people out there who know the answer.