SSL write/read performance

[Matt Caswell]

On 10/04/2019 10:32, valmiki wrote:
> Hi All,
> 
> I'm trying to understand server and client code over tcp using openssl.
> 
> How does the flow work when we do SSL_write or SSL_read.
> 
> SSL_write -> send buffer to kernel crypto subsystem -> take encrypted buffer and send it over network socket.
> 
> Is the above understanding correct ?

No, this isn't correct. All crypto is done in user space* using libcrypto.

Matt

* Actually there is a new option in master where the kernel does the TLS
encryption/decryption - but it is not on by default, and if used the kernel does
the IO too.


> 
> If its correct we have following context switch from user to kernel space and vice versa
> 
> -> open ssl libary to kernel crypto subsystem
> 
> -> kernel crypto subsystem to ssl library
> 
> -> ssl library to network subsystem
> 
> Does this mean for sending a buffer we need to three context switches from user to kernel and vice versa ?
> 
> Doesn't this effect performance ?
> 
> Please correct me if my understanding is wrong.
> 
> Regards,
> valmiki
> 
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