iscsi_create_context: improve ISID randomness

The current random seed for determining a new context's ISID is
calculated by XOR'ing time(), getpid() and "iscsi". When invoked from
iscsi_reconnect(), all three inputs are likely to be identical,
resulting on identical ISIDs.

That happens because iscsi_reconnect() malloc()s a temporary "iscsi"
which is then free()d at the end of the call. Successive calls to
malloc() (from that function) are therefore likely to reuse the same
address for the context.

When multiple sessions are used for different LUNs of the same target,
and reconnects happen within the same second (the precision given by
time()), then multiple login attempts will happen with identical values,
violating the ISID RULE as described in Section 3.4.3 of RFC3270.

This fixes the issue by introducing a sequence number to the ISID seed
generation.

Signed-off-by: Felipe Franciosi <felipe@nutanix.com>

lib/init.c

@@ -153,6 +153,7 @@ iscsi_create_context(const char *initiator_name)
 {
 	struct iscsi_context *iscsi;
 	size_t required = ISCSI_RAW_HEADER_SIZE + ISCSI_DIGEST_SIZE;
+	static uint32_t ctx_seq = 0;
 	char *ca;
 
 	if (!initiator_name[0]) {
@@ -176,7 +177,7 @@ iscsi_create_context(const char *initiator_name)
 
 	iscsi->fd = -1;
 
-	srand(time(NULL) ^ getpid() ^ (uint32_t) ((uintptr_t) iscsi));
+	srand(time(NULL) ^ getpid() ^ (uint32_t) ((uintptr_t) iscsi) ^ ctx_seq++);
 
 	/* initialize to a "random" isid */
 	iscsi_set_isid_random(iscsi, rand(), 0);