pbuf_freep;

The code pbuf_free(p); is used to free a pbuf structure in the lwIP network stack.

The pbuf_free() function is used to deallocate a pbuf structure and release the memory associated with it. It takes a pointer to the pbuf structure as an argument and frees the memory.

Here, p is a pointer to the pbuf structure that needs to be freed. After calling pbuf_free(p), the memory occupied by the pbuf structure will be released and can be reused for other purposes.

It is important to note that pbuf_free() only frees the pbuf structure itself, not the payload data it may be pointing to. If the payload data is dynamically allocated, it needs to be freed separately before calling pbuf_free()