Archisman Maitra

💻 Principal Engineer Palo Alto Networks ▪️Ex-MRVL Ex-CSCO▪️
10+ Embedded SW ▪️Networking▪️AI ▪️
Jack of Few Trades▪️🌍✈️📸♟️🏏 💹

[Archisman Maitra @archisM001]

🛜Embedded s/w for Networking 🛜 ✅Part 1

🚀Netfilter🚀

It's a Linux kernel framework that allows for packet filtering, translation, manipulation tasks via hooks within the kernel's networking stack to intercept and process network packets at various stages as followed:-

1⃣ PRE_ROUTING- It's triggered when a packet enters the network stack (After getting received by the network interface), before any routing decisions are made.

2⃣ LOCAL_IN - Its triggered for packets destined for the local host after the routing decision.

3⃣ FORWARD - Its triggered for packets that are neither destined for nor originated from the local host but are being forwarded.

4⃣ LOCAL_OUT - Its triggered for packets generated by the local host before they are sent out of the network stack

5⃣ POST_ROUTING - It's triggered just before a packet leaves the network stack, after routing decisions and any modifications.

When a packet passes various stages of the hooks, actions like accept, drop, reject, queue (to user space), modify, log or return are taken on the packets defined by Linux tools such as iptables.

🤏 For example, an iptables rule might look like: iptables -A INPUT -p tcp --dport 80 -j ACCEPT (accepts TCP packets to port 80).

Hook Dependency: The available actions depend on the hook (e.g., NAT actions like SNAT are only valid in POST_ROUTING, while DNAT is valid in PRE_ROUTING).

❓What is INPUT here in the above example?

📌In next episode, we will deep dive into the purpose and real life use case of each hook stage, chains in netfilter and few examples of packet flows.

#CyberSecurity #Firewall #linuxtechtips #linuxcommands #networkingprotocols #NetworkSecurity #TCPIP #Switching #routingalgorithms #embeddedcomputing

[Archisman Maitra @archisM001]

Hi @IndiGo6E, Me and my wife who is pregnant, travelled from BLR to CCU on 6E442 on 13th June, 2026. We had an excelleng experience on board and the crew headed by Apoorva and Angelina took amazing care of my wife. Giving a shoutout to them!!

[Prosenjit @mitrapredator]

December 1998 - Kolkata

[Facts @BefittingFacts]

Now Mumbai is facing a water crisis, and companies are moving towards work from home.

Big companies should consider relocating their headquarters from Mumbai to Kolkata.

The biggest benefit is that the newly elected government is desperate for investment, so companies are likely to get the best possible deals and incentives.

There are also cheaper office rents and better connectivity, especially once the Garia–Airport Metro becomes operational.

Ghar Wapsi of companies!

[Archisman Maitra @archisM001]

@jaintarang11 @Kenu73 I stayed there as well, very close to Palladium

[Archisman Maitra @archisM001]

@rajuidesai @smartindiainc1 $ABVE got delisted. US is a brutal market.

[Archisman Maitra @archisM001]

@AH94RAR @GrindeOptions It may get delisted if 20F not filed soon

[The West Bengal Index @TheBengalIndex]

Obituary written for half a century, came back in the mainstream in 2026.

Still among the three largest cities in India by population and economy.

When you're big, you're big.

[Archisman Maitra @archisM001]

Today's innings by Sooryavanshi reminds of the tale of Abhimanyu. Only Sooryavanshi was able to break the Chakravruha @IPL

[Archisman Maitra @archisM001]

@BJP4Bengal @CMO_Benga released the Annapurna scheme to honour the election promise too early in my opinion. Training of door to door municipal stuff should have been done for a month along with detailed financial audit before releasing to the public. People on ground are paranoid.

[Archisman Maitra @archisM001]

@Thangaul @Akshat_World Makes sense.

[Archisman Maitra @archisM001]

@rakeshonmoon @Akshat_World No One Size fits all rule. Agree

[Archisman Maitra @archisM001]

@Thangaul @Akshat_World Yes I am doing that UCITS etf via IBKR. But how much to keep as concentration vs how much to diversify is a question which I ponder upon every vesting.

[Archisman Maitra @archisM001]

Hoping it's not a fake Pump.

[Archisman Maitra @archisM001]

$ABVE any chatters today?

[Archisman Maitra @archisM001]

Tax benefits on availing family domestic tourism, can increase domestic tourism consumption. @nsitharaman @FinMinIndia @narendramodi

[Archisman Maitra @archisM001]

@johnyacex From where are you getting the chatter

[Archisman Maitra @archisM001]

@Kaspasinceday1 It can get delisted now

[Suvendu Adhikari @SuvenduWB]

HISTORIC TRIUMPH 🏆
EAST BENGAL ARE THE ISL CHAMPIONS 🔴🟡

Heartiest Congratulations to East Bengal FC for lifting the Indian Super League (ISL) trophy. This is a momentous day for millions of Red and Gold fans & supporters across West Bengal and the globe.
You have paid tribute to the true spirit of Bengal's football heritage. The Players, the Coaching Staff, and Management have proven what can be achieved with sheer dedication and grit.

A special shoutout to Mohun Bagan as well who finished 2nd with same points but got edged out due to goal difference.

Football is synonymous with West Bengal, both the Teams have made us proud.

@eastbengal_fc

[Archisman Maitra @archisM001]

@neilsbhatia Yes it's frustrating