Everything down to Turkey is very straightforward.
You may possibly have difficulties getting an Iranian visa depending on your nationality (I applied for one in May 2008 and was kept waiting to the point where it became irrelevant to pursue it) but it looks like the recent US presidential election result will improve relations. (The Iranian president sent a congratulatory message to the president-elect and OB has offered Iran direct talks on its nuclear programme.)
Yemen into Djibouti is the normal route of entry into Africa, followed by Ethiopia then Sudan. You should check the security situation in Eritrea if you specifically want to go there. There are border conflicts with its neighbours and travel permits are required to leave Asmara.
For Libya you will need to arrange a visa through a local tourism organisation and pay for a guide or obtain a transit visa which restricts you to the coast.
As you mention, Tunisia to Europe (e.g. Sicily) by ferry is currently the only way to complete your journey (without heading south).
You can get more specific information on the above by searching for HU threads on each country.
Stephan
|