[lwip-devel] [bug #49914] lwip_sendmsg uses PBUF_REF pbufs

[Joel Cunningham]

Follow-up Comment #6, bug #49914 (project lwip):

David,

Thanks for correcting my memory of the TCP retransmit/output behavior. I had
provided some discussion in task #7896 about the pitfalls of not handling this
case (which I had seen with another embedded stack) and had remembered
incorrectly for LwIP. Given that LwIP is handling the reference count, I agree
the netif should not have to copy any PBUF_RAM pbufs

I like the idea of a convenience function that handles the complexity for the
driver.  Maybe something like pbuf_clone() could be used to handle both the
check and copying. This would be called when the netif needs to keep the pbuf
chain past execution of the output function. This would increment the
reference count on PBUF_RAM and make copies PBUF_REF (or copy the entire chain
in the REF case if we prefer that behavior)





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