Re: [lwip-users] UDP sending more than 1472 bytes with raw API

[Sylvain Rochet]

Hi Sergio,

On Fri, Jul 29, 2016 at 11:20:15AM -0300, Sergio R. Caprile wrote:
> >>* UDP is message oriented, so you have to split your data in datagrams, *
> >>* because a datagram must fit on an IP datagram on an Ethernet frame.*
> 
> > No, IP supports fragmentation, and lwIP supports fragmented IP packets
> > using the IP_FRAG compilation option.
> 
> Good point, I'm too used to stacks not supporting fragmentation quite
> well, and memory constraints where a full size Ethernet frame is a bit
> of a luxury...
> 
> As per the OP question, he then could get away with IP_FRAG and a a 
> big enough pbuf if he can afford it ?
> 
> lwipopts.h --> #define IP_FRAG 1
> 
> application --> udp_send(pcb, p);

Yes, as long as its receiving target supports fragmented IP packets of 
at least the size sent as well ;-)

Sylvain

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