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Re: [lwip-devel] [bug #19225] bind, connect, and sendto should verify in


From: Jonathan Larmour
Subject: Re: [lwip-devel] [bug #19225] bind, connect, and sendto should verify input paramers
Date: Thu, 12 Apr 2007 01:20:37 +0100
User-agent: Mozilla Thunderbird 1.0.8-1.1.fc3.4.legacy (X11/20060515)

Sorry this is an old topic, but I thought it worth a comment...

Simon Goldschmidt wrote:
[about the netconn API]
The only benefit seems to be the zero-copy on receive. TCP sending with
copy=0 (zero copy send) is rare since you must have real static (or ROM)
data.

I would say there is more benefit than that for those who are concerned about low memory use. A lot of our users are wanting to use lwIP to provide a web server for management of the embedded device, or getting status. Web pages for device management are usually full of constant never-changing data, which can happily live in ROM. It is more work and if you have more memory you can avoid it, but if you have a small System-on-Chip you have no choice.

For UDP, pbufs are chainable, which means you can benefit even if only _some_ of the data to send is in ROM - just those pbufs can be of type PBUF_ROM. Although the only good application I know of for this is TFTP.

Jifl
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