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richardh
richardh
Associate III
June 3, 2020
Question

LWIP - Read my IP address

  • June 3, 2020
  • 4 replies
  • 15533 views

I have found examples online searching under LWIP such as 

// What is our current IP address?
//
ulIPAddr = lwIPLocalIPAddrGet();

but I cannot find the function in the source code, or any other reference to reading my IP address. I would like to be able to read it regardless of whether I'm static or DHCP.

This topic has been closed for replies.

4 replies

richardh
richardhAuthor
Associate III
June 3, 2020

Okay, so with a little more hunting, I have

 extern struct netif gnetif;
 
 local_IP = gnetif.ip_addr.addr;
 
printf("IP %d.%d.%d.%d\n\r",(local_IP & 0xff), ((local_IP >> 8) & 0xff), ((local_IP >> 16) & 0xff), (local_IP >> 24));

but if its DHCP, how do I know if the address is initialised?

Piranha
Piranha
Principal III
June 3, 2020

To get IP address, use netif_ip4_addr() and ip4_addr_get_u32(). When using DHCP, use ip4_addr_isany_val() to determine if it's assigned. And take a look at lwIP's bunch of similar functions and macros.

richardh
richardhAuthor
Associate III
June 4, 2020

Thats spot on - thank you!

More questions though, how do I read the subnet mask and MAC address also?

Finally can I set the host name manually as well? so if I look at the DHCP server reservations pool I can easily spot my device by name?

richardh
richardhAuthor
Associate III
June 5, 2020

as an addition, how do I set the MAC Address?

I can find it hardcoded in ethernet.c which is fine if this was going to be a single unit, but if by some miracle it went into production then what is the mechanism to allow you to update it?

Host name I have figured out, I was just reading it wrong.

 extern struct netif gnetif;
 
 local_SubNet = ip4_addr_get_u32(netif_ip4_netmask(&gnetif));
 
 local_Gateway = ip4_addr_get_u32(netif_ip4_gw(&gnetif));

Piranha
Piranha
Principal III
August 28, 2022

> I can find it hardcoded in ethernet.c which is fine if this was going to be a single unit, but if by some miracle it went into production then what is the mechanism to allow you to update it?

Then you write a normal code, which updates the MAC address in both - the ETH registers and NETIF structure.

FPaul.3
FPaul.3
Visitor II
August 24, 2022

Credit to GitHub copilot, which recommends me: 

printf("IP address: %s\n", ip4addr_ntoa(&gnetif.ip_addr));

result:

IP address: 192.168.1.63

Piranha
Piranha
Principal III
August 28, 2022

More correct version:

printf("IP address: %s\n", ip4addr_ntoa(netif_ip4_addr(&gnetif)));

Pavel A.
Pavel A.
Super User
August 28, 2022

> Credit to GitHub copilot

Few years ago when I first seen the Cube, I hoped it would evolve in the direction of the Copilot: a tool that knows all the reference manuals, all errata, trained on all the examples, backed by a serious AI. Alas.

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