ICMPINFO(1)

🦋 icmpinfo — interpret ICMP messages ✨

okay so real quick, this is a General Commands Manual page, and it's about a lil tool called icmpinfo, and honestly? it's a whole vibe if you're into network forensics. buckle up bestie 💖

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🌸 NAME 🌸

icmpinfo — interpret ICMP messages. that's it, that's the whole name. short, iconic, does what it says on the tin 💅

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⭐ SYNOPSIS ⭐

icmpinfo [-v[v[v]]] [-n] [-p] [-s] [-l] [-k]

look at her. all those lil brackets stacking up like a tower. she's flexible, she's lowkey mysterious, she's icmpinfo 🎀

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🔥 DESCRIPTION 🔥

so icmpinfo is a tool for looking at the ICMP messages received on the running host. that's the whole job. it sits there, it watches the ICMP traffic landing on your machine, and it tells you what's up.

and like — it's not just for curiosity, no cap. you can use it to detect and record 'bombs' as well as various network problems. so it's giving security tool, it's giving diagnostic tool, it's giving main character energy 💀

the output format is as follows (all on one line, bestie, don't panic when it looks cramped):

MMM DD HH:MM:SS ICMP_type[sub-type]
   < sender_ip [sender_name] > unreach_ip [unreach_name]
   sp=source_port dp=dest_port seq=sequence sz=packet_size

in normal operation, icmpinfo will only report on "weird" packets — mainly icmp_unreachable. so by default she's picky. she's not gonna spam you with everything, she's just gonna flag the weird stuff. and honestly? respect 🫶

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✨ OPTIONS ✨

okay so here's every single flag, no skipping, no summarizing, we're doing this properly because i love you 🧚

• -v — give information about all icmp packets, excepts pings. so like, everything but the ping-y ones. that's the first v, we're warming up 🔥
• -vv — give about pings too (i.e. icmp_echo_reply). now the pings get to come to the party too. double v, double the tea 🍓
• -vvv — include an ascii/hex dump of each packet. triple v and now we're DUMPING bytes. this is the maximalist option, she ate 💅
• -n — avoid name queries, just give IP addresses. and like, use this option when running unattended on name server hosts (to avoid possible looping) — that's a real caveat, don't sleep on it 😭
• -p — avoid port number to service name decoding. numbers stay numbers, no name translation, we keep it raw ✨
• -s — show the interface ip that received the packet. useful only if your host has several network interfaces. in this case an -my_ip [my_name] is added between the sender and unreach ip and name fields. multi-nic girlies, this one's for you 🌈
• -l — forks and use the syslog(3) facility to record events (recommended use). root only option — like, fr fr, you need to be root for this one 👑
• -k — kills the background process started with the -l option. the clean-up crew. the "we're done here" button 🎀

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💀 WARNINGS 💀

the packet decoding is planned for ICMP Unreachable outputs and might not be significant for all other Icmp types. so like — don't come for her if the other ICMP types look weird in the dump, that's not what she was built for, okurrr 🙈

output can be shorter when implied by the packet size or the icmp type. so if a line looks incomplete, that's not a bug, that's just the packet being small or the type being a certain way. vibe check passed, nothing to worry about 💜

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🫶 AUTHOR 🫶

Laurent Demailly <dl@hplyot.obspm.fr>. Free software. we stan a generous open-source icon ⭐

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and that's the page!! this whole thing is from dl's free utilities, version V1.11, dated 17 August 1995 — yes, 1995, she's vintage and she's still slaying 😭💖 go read your packets bestie, ily 🦋