UPDATE (9/16/2014): I encourage people to read Bruce Schneier’s post regarding surreptitious tampering of computer chips, which includes hardware random number generators. It’s nearly impossible to know that a hardware RNG hasn’t been tampered with at the time of manufacture to facilitate a backdoor. Therefore, it might be worth sticking with a software RNG, as is the default behavior in Raspbian.
The Broadcom System on a Chip (SoC) in the Raspberry Pi features a hardware random number generator that can be used as a high-quality source of random numbers. This might be worth enabling if you’re using OLSRD in a secure mode. The secure mode causes the node to exchange cryptographic messages with other nodes in the mesh network. Strong cryptography benefits greatly from the use of a high quality random number generator. Also, the system load should decrease since the task of producing random numbers is offloaded to a dedicated hardware device.
Here’s a link to a quick how-to with the steps for enabling the hardware random number generator on the Raspberry Pi: