Bug Fix: Yaklang Failed To Inherit IP Address

Aug 14, 2025 by Aria Freeman 46 views

[Bug]: Failed to Inherit IP: IP Address Not Set

Hey guys,

We've got a bug report on our hands that we need to dive into. It's related to the Yaklang engine and involves an issue where the system fails to inherit an IP address during port fingerprint scanning. This can be a real headache, so let's break down the details and see what's going on.

Understanding the Bug: "Failed to Inherit IP"

In the realm of network scanning, one common challenge is ensuring the tool can properly set up its network interfaces. Our main keyword here is the "failed to inherit IP" error, which pops up when the Yaklang engine, specifically version V1.4.3-beta6, tries to create a virtual network interface (veth) for port fingerprint scanning. This error, "nic[vethXXXXXXX] failed to inherit ip: ip address not set", indicates that the virtual network interface being created isn't getting an IP address assigned to it, causing the scanning process to fail. This issue is particularly critical because port fingerprint scanning is a fundamental technique for identifying open ports and services on a target system, which is crucial for vulnerability assessment and network security.

The root cause of this issue lies in the way the Yaklang engine manages network interfaces during the scanning process. When the engine attempts to create a veth interface, it expects to be able to assign an IP address to it. However, if this process fails, the interface remains without an IP address, leading to the reported error. Several factors could contribute to this failure, such as insufficient permissions, network configuration issues, or bugs within the engine's network management code. For instance, if the user running the Yaklang engine lacks the necessary privileges to create and configure network interfaces, the IP address assignment may fail. Similarly, if the underlying network configuration is misconfigured or if there are conflicts with existing network settings, the engine might be unable to assign an IP address to the veth interface. Addressing this bug is essential to ensure the reliability and accuracy of the port fingerprint scanning functionality.

To resolve the "failed to inherit IP" error, a multifaceted approach is required. First, it's crucial to verify that the user running the Yaklang engine has sufficient privileges to create and configure network interfaces. This may involve adjusting user permissions or running the engine with elevated privileges. Second, the network configuration should be thoroughly checked to ensure there are no conflicts or misconfigurations that could prevent IP address assignment. This includes verifying that the network interface is properly configured, that there are no IP address conflicts, and that the routing tables are correctly set up. Finally, the Yaklang engine's network management code should be examined for potential bugs or inefficiencies that could be causing the issue. This may involve debugging the engine's code, reviewing the network interface creation and configuration logic, and identifying any areas where errors could occur. By addressing these potential causes, we can effectively resolve the "failed to inherit IP" error and ensure the smooth operation of the port fingerprint scanning functionality.

Reproducing the Bug

To get a handle on this, we need to be able to reproduce it reliably. Here are the steps that were used to trigger the bug:

Set up the Environment: Fire up an Ubuntu 22.04.5 LTS (Jammy Jellyfish) system. This is the specific environment where the bug was initially encountered, so it's important to match it.
Start Yak GRPC: Launch the Yaklang GRPC server with the following command:
```
yak grpc --host 0.0.0.0 --port 8087 --secret xxxx --tls
```
This command starts the Yaklang GRPC server, which is the component responsible for handling scanning requests. The --host, --port, --secret, and --tls flags configure the server's network settings, authentication secret, and TLS encryption, respectively. It is crucial to ensure that these flags are set correctly to establish a secure connection between the server and the client.
Initiate a Scan: From a Mac client, start a scan against a specific IP address. This action triggers the creation of virtual network interfaces on the Linux server, which is where the bug occurs.
Check the Logs: Monitor the logs on the Linux server. You should see the error message:
```
[ERRO] 2025-08-14 03:58:04 [netvm:158] nic[veth0a47a12] failed to inherit ip: ip address not set
```
This error message confirms that the virtual network interface creation process failed to inherit an IP address, indicating the presence of the bug. The error message provides valuable information for debugging, including the timestamp, the module where the error occurred (netvm), the line number, and the name of the network interface that failed to inherit an IP address (veth0a47a12). This information can be used to trace the error back to the specific code responsible for network interface creation and IP address assignment.

By following these steps, you can consistently reproduce the "failed to inherit IP" bug and gain a deeper understanding of its behavior. Reproducibility is essential for debugging and fixing the bug effectively. Once the bug can be reliably reproduced, developers can investigate the underlying causes and implement appropriate solutions.

Diving into the Logs

The provided logs give us some clues. Let's break them down:

[INFO] 2025-08-14 03:58:00 [netvm_entry:91] start to create pcap endpoint default mac: 76:18:10:37:e4:ba
[INFO] 2025-08-14 03:58:02 [pcap_endpoint:224] start to attach pcap endpoint outbound loop and inboundloop
[INFO] 2025-08-14 03:58:02 [pcap_endpoint:263] start to execute inbound loop with mtu: 1700
[INFO] 2025-08-14 03:58:02 [netvm_entry:91] start to create pcap endpoint default mac: ea:33:b8:a3:c8:d1
[INFO] 2025-08-14 03:58:04 [pcap_endpoint:224] start to attach pcap endpoint outbound loop and inboundloop
[INFO] 2025-08-14 03:58:04 [pcap_endpoint:263] start to execute inbound loop with mtu: 1700
[ERRO] 2025-08-14 03:58:04 [netvm:158] nic[veth0a47a12] failed to inherit ip: ip address not set
[INFO] 2025-08-14 03:58:04 [netvm_entry:91] start to create pcap endpoint default mac: 02:6c:da:3a:7d:24
[INFO] 2025-08-14 03:58:06 [pcap_endpoint:224] start to attach pcap endpoint outbound loop and inboundloop
[ERRO] 2025-08-14 03:58:06 [netvm:158] nic[veth628e83c] failed to inherit ip: ip address not set
[INFO] 2025-08-14 03:58:06 [pcap_endpoint:263] start to execute inbound loop with mtu: 1700
[INFO] 2025-08-14 03:58:06 [netvm_entry:91] start to create pcap endpoint default mac: d6:21:76:26:ec:29
[INFO] 2025-08-14 03:58:08 [pcap_endpoint:224] start to attach pcap endpoint outbound loop and inboundloop
[ERRO] 2025-08-14 03:58:08 [netvm:158] nic[vethddb1087] failed to inherit ip: ip address not set
[INFO] 2025-08-14 03:58:08 [netvm_entry:91] start to create pcap endpoint default mac: f2:be:f2:11:1b:3b
[INFO] 2025-08-14 03:58:08 [pcap_endpoint:263] start to execute inbound loop with mtu: 1700
[INFO] 2025-08-14 03:58:11 [pcap_endpoint:224] start to attach pcap endpoint outbound loop and inboundloop
[ERRO] 2025-08-14 03:58:11 [netvm:158] nic[veth612c03a] failed to inherit ip: ip address not set
[INFO] 2025-08-14 03:58:11 [pcap_endpoint:263] start to execute inbound loop with mtu: 1700
[INFO] 2025-08-14 03:58:11 [netvm_entry:91] start to create pcap endpoint default mac: 2e:0e:96:46:2a:e3
[INFO] 2025-08-14 03:58:13 [pcap_endpoint:224] start to attach pcap endpoint outbound loop and inboundloop
[INFO] 2025-08-14 03:58:13 [pcap_endpoint:263] start to execute inbound loop with mtu: 1700
[INFO] 2025-08-14 03:58:13 [netvm_entry:91] start to create pcap endpoint default mac: fe:c7:02:45:d6:f5
[INFO] 2025-08-14 03:58:15 [pcap_endpoint:224] start to attach pcap endpoint outbound loop and inboundloop
[ERRO] 2025-08-14 03:58:15 [netvm:158] nic[vetha939133] failed to inherit ip: ip address not set

Here's what we can gather:

The system is creating pcap endpoints, which are used for capturing network traffic.
It's setting up inbound and outbound loops, likely for sending and receiving packets.
The key error, "nic[vethXXXXXXX] failed to inherit ip: ip address not set", appears repeatedly. This tells us that the creation of virtual network interfaces (vethXXXXXXX) is failing because they aren't getting IP addresses.
The errors occur in the netvm module, specifically around line 158, which suggests the issue is within the network virtualization management code.

This error message is the central clue for diagnosing the problem. It indicates that the virtual network interfaces created by the Yaklang engine are not being assigned IP addresses, which is essential for their proper functioning. The repetition of this error message suggests that the issue is systemic and affects multiple interfaces, rather than being an isolated incident. Further investigation is needed to determine why the IP address assignment is failing and what steps can be taken to rectify the problem. This might involve examining the network configuration, the code responsible for IP address assignment, and any dependencies or external services that could be interfering with the process.

Expected Behavior

The expected behavior is straightforward: the port fingerprint scan should complete without errors. The virtual network interfaces should be created, assigned IP addresses, and used for scanning. The absence of the "failed to inherit IP" error is a key indicator of the system functioning correctly. In a successful scenario, the Yaklang engine would seamlessly create the necessary veth interfaces, configure them with appropriate IP addresses, and utilize them to perform the port fingerprint scanning operations. This would enable the engine to accurately identify open ports and services on the target system, providing valuable information for security assessments and network analysis. The smooth operation of the network interface creation and IP address assignment process is crucial for the overall reliability and accuracy of the scanning process.

When the system functions as expected, the logs should reflect the successful creation and configuration of the virtual network interfaces. There should be no error messages related to IP address assignment or network interface creation. Instead, the logs should show information about the successful creation of the veth interfaces, their configuration with IP addresses, and their utilization in the scanning process. This includes details such as the interface names, IP addresses assigned, and any other relevant network parameters. The absence of errors and the presence of successful operation messages in the logs are strong indicators that the system is functioning as intended and that the port fingerprint scan is proceeding without any issues. Therefore, the expected behavior is not only the completion of the scan without errors but also the clear and positive confirmation of successful network interface management in the logs.

Environment

Operating System: Linux (specifically, Ubuntu 22.04.5 LTS)

This is important because the bug might be specific to the Linux environment or even to a particular version of Ubuntu. The differences in network management and configuration across operating systems can lead to variations in how software behaves, and this bug could be related to such differences. For instance, the way virtual network interfaces are created and configured might differ between Linux and Windows, and the specific tools and libraries used for network management could also vary. Therefore, it is essential to consider the operating system as a key factor in understanding and resolving the bug. Additionally, the specific version of the operating system, such as Ubuntu 22.04.5 LTS, might introduce further nuances. Different versions of an operating system can have variations in their kernel, network stack, and other system components, which could affect the behavior of network-related software. Therefore, specifying the operating system and its version provides valuable context for developers and helps narrow down the potential causes of the bug.

Possible Causes and Solutions

Based on the information we have, here are some potential causes and how we might address them:

Permissions Issue: The Yaklang engine might not have the necessary permissions to create network interfaces or assign IP addresses. This is a common issue when dealing with network-related operations, as they often require elevated privileges. To address this, ensure that the user running the Yaklang engine has the appropriate permissions, such as being a member of the netdev group or having CAP_NET_ADMIN capabilities. Alternatively, you might need to run the engine with sudo or configure it to run as a privileged user. However, running with elevated privileges should be done cautiously and only when necessary, as it can introduce security risks.
Network Configuration: There could be a conflict in the network configuration, preventing the engine from assigning an IP address. This could occur if there is an existing network interface with the same IP address or if the network's subnet is already fully utilized. To resolve this, review the network configuration to ensure there are no conflicts and that there are available IP addresses within the subnet. You might need to adjust the network configuration, such as changing the IP address range or subnet mask, to accommodate the virtual network interfaces created by the engine. Additionally, check for any firewall rules or network policies that might be blocking the assignment of IP addresses to the virtual interfaces.
Bug in Yaklang Engine: There might be a bug in the Yaklang engine's network management code. This is always a possibility, especially with beta software. If this is the case, the bug needs to be identified and fixed in the engine's code. This might involve debugging the code, reviewing the network interface creation and configuration logic, and identifying any areas where errors could occur. If a bug is found, it should be reported to the Yaklang developers so that they can address it in a future release. In the meantime, a workaround might be necessary to mitigate the issue, such as manually configuring the network interfaces or using a different scanning tool.

Next Steps

To get this fixed, here's what needs to happen:

Verify the Reproducibility: We need to ensure that the bug can be consistently reproduced across different environments.
Investigate the Code: Developers need to dive into the Yaklang engine's code, specifically the netvm module, to understand how it creates and configures network interfaces.
Test Solutions: Once a potential cause is identified, solutions need to be tested thoroughly to ensure they fix the bug without introducing new issues.

Conclusion

The "failed to inherit IP" bug is a serious issue that prevents the Yaklang engine from performing port fingerprint scans correctly. By understanding the bug, how to reproduce it, and the potential causes, we can work towards a solution. We'll keep you updated on the progress as we investigate and resolve this issue. Stay tuned, and thanks for reporting the bug!