PCAP_OPEN_LIVE(3)

🎀 NAME 🎀

okay so this is the PCAP_OPEN_LIVE(3) manual page, and pcap_open_live(3) is literally here to open a device for capturing. bestie, it's the glow-up that gets you a packet-capture handle so you can look at packets on the network. 💖

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✨ SYNOPSIS ✨

no cap, here's the exact spellbook entry:

#include <pcap/pcap.h>

char errbuf[PCAP_ERRBUF_SIZE];

pcap_t *pcap_open_live(const char *device, int snaplen,
    int promisc, int to_ms, char *errbuf);

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🦋 DESCRIPTION 🦋

pcap_open_live() is used to obtain a packet capture handle to look at packets on the network. main character energy fr fr. 💅

• device — a string that specifies the network device to open. on all supported Linux systems, as well as on recent versions of macOS and Solaris, a device argument of "any" or NULL can be used to capture packets from all network interfaces.

🫶 okay but listen: that "any" / NULL situation should not be confused with all available capture devices as seen by pcap_findalldevs(3), which may also include D-Bus, USB etc. that's a different vibe, iykyk.

• snaplen — specifies the snapshot length to be set on the handle. if the packet data should not be truncated at the end, a value of 262144 should be sufficient for most devices, but D-Bus devices require a value of 128MB (128*1024*1024). yes, that's the assignment. 💀
• promisc — specifies whether the interface is to be put into promiscuous mode. if promisc is non-zero, promiscuous mode will be set, otherwise it will not be set. simple as that. ✨
• to_ms — specifies the packet buffer timeout, as a non-negative value, in milliseconds. (see pcap(3) for an explanation of the packet buffer timeout.) she's on a timeline, bestie. ⏳
• errbuf — a buffer large enough to hold at least PCAP_ERRBUF_SIZE chars. give her room to breathe. 🌸

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🔥 RETURN VALUE 🔥

pcap_open_live() returns a pcap_t * on success and NULL on failure. if NULL is returned, errbuf is filled in with an appropriate error message. 😭

errbuf may also be set to warning text when pcap_open_live() succeeds. to detect this case, the caller should store a zero-length string in errbuf before calling pcap_open_live() and display the warning to the user if errbuf is no longer a zero-length string. that's the sneaky little vibe check, and yes you have to do it. 👑

💅 warning: don't skip the zero-length-string setup unless you want to miss the warning text. the manual is literally telling you the move.

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🌈 SEE ALSO 🌈

• pcap_create(3)
• pcap_activate(3)

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this iconic little page is from the PCAP_OPEN_LIVE(3) manual, under the Library Functions Manual, dated 4 March 2024. periodt. mwah 💋🎀