Summary-Cache Enhanced ICP Implementation

The implementation adds in the following new source files to Squid 1.1.14's code:

• md5.h, md5.c, md5string.c: code from RSA for calculating the MD5 signature of an arbitrary-length string;

• sc_hashkeys.c: given an url, calculates the hash function values by first calculating the MD5 signature, and then using successive groups of bits;

• sc_broadcast.c: handles packing and unpacking summary updates into a ICP-formated message, and sending the updates to neighbors;

• sc_probe.c: provide routines that the ICP uses to determine whether a document is at a remote cache. ICP usually calls peerWouldBePinged to determine whether a query should be sent to a neighbor. We changed the name to peerWouldBePinged_forURL.

  The file also has routines to update the summary based on received update message.

  There are two versions of sc_probe.c: sc_probe.c. and sc_probe.msb.c. sc_probe.msb.c support the format of update message where the most significant bit of each update entry indicate whether the bit should be set to 0 (in the case of the MSB being 1) or 1 (in the case of the MSB being 0). It is less tested, but can handle UDP message loss better.

• sc_updates.c: contains all the routines needed to maintain the local bloom filter and to construct update messages. Again, there are two versions, sc_updates.c and sc_updates.msb.c.