There were a total of 5 rounds. The process started at 10 am and ended at 4:45 p.m.

First Round (1hr 30min): Total focus was to understand the current project which I was working on. Then, digging into questions about the current project. A complete explanation was required, and then questions were asked about the different data structures used in the project. I told them about hash tables, which they asked me to implement. Be thorough with the current project.

Second Round (1hr 15 min): This was the programming round. They asked me 2-3 questions related to multithreading, mutexes, and semaphores, and their implementation. Then, they asked me 2-3 questions on bitwise operators (set a bit, invert the bit). Then came questions related to linked lists (find a loop) and trees (implement BST, depth of a tree).

Third Round (1hr 15 min): Again, they started off with the current project. Then, they asked me about the packet flow if you type google.com. They wanted to know about the application-side HTTP, which I did not have an idea about. I told them about the L2-L3 flow. Then, they asked about different sections going deep into the kernel and TCP/UDP flow implementation in the kernel.

Fourth Round (1hr 30min): They asked me again about the project, different data structures, linked lists, trees, and to implement tries and hashes. They were looking for people having knowledge in all data structures (trie, hash map). Networking questions were about VLAN and IP routing.

Fifth Round (1hr 45min): This was the manager round. They asked a lot of questions about the kernel, volatile variables, and optimization. They made two or three programs and asked me to find the errors. They asked about IP fragmentation and reassembly.

I was really exhausted after the process. I thought there would be an HR round, but that did not happen. I was told HR would get back to me.

Experience was fine. I answered most of their questions but am not sure about what was expected. They should inform where the interview went wrong.

Why do we use volatile?

Different header fields.

TCP, UDP headers and their differences. Flow control.

Tries and hash maps.

Implement multithreading. Use mutexes and semaphores in the program.

Find the depth of the tree.