primarily used with TCP SYN and RST packets and such packets are less than
the smallest sized packet that an IP stack is allowed to fragment, we simply
set ip_id to 0 for all packets 68 bytes or less.
because that's just going to cause problems down the road. (Suppose
we can have two CPUs in the network stack someday?) Instead, use
sockaddr_in_init() to initialize a sockaddr_in on the stack.
Use ifreq_setaddr() to initialize ifreq.ifr_addr.
the decapsulator dispatch changes in 2001. Problems found and fixed
by Christine Jones of BBN. Specifically:
Check for a packet's protocol to be ENCAP_PROTO, not AF_INET.
Remove one-back cache for last vif, because vif_encapcheck is called
for each vif, rather than being expected to find the appropriate vif.
The cache usage caused packets to be input on the wrong vif and hence
usually dropped.
In vif_encapcheck, verify the local source as well. While mrouted
endeavors not to create multiple tunnels with a peer, a packet
arriving with the wrong local address is still wrong and should not be
accepted. (This is a correctness nit, not a security issue.) Order
checks to fail quickly for packets being checked to see if they match
a vif other than the one they belong on (essentially, check peer
source address in outer header first).
Claim 69 bits of match (32 each from outer src/dst and 5 from checking
that inner dst is within 224/5). This should result in the vif having
a higher priority for multicast packets compared to a parallel gif(4)
tunnel, and that both seems appropriate if both are configured and
seems to match the semantics expected by the decapsulator dispatch
machinery.
(These changes were made in 2.99.15 and about a dozen nodes are
running them with many vifs. ip_mroute.c has not changed
significantly since then (February 2005) and the changes applied
cleanly to current and compile cleanly.)
* Include "opt_inet.h" everywhere IP-ids are generated with ip_newid(),
so the RANDOM_IP_ID option is visible. Also in ip_id(), to ensure
the prototype for ip_randomid() is made visible.
* Add new sysctl to enable randomized IP-ids, provided the kernel was
configured with RANDOM_IP_ID. (The sysctl defaults to zero, and is
a read-only zero if RANDOM_IP_ID is not configured).
Note that the implementation of randomized IP ids is still defective,
and should not be enabled at all (even if configured) without
very careful deliberation. Caveat emptor.
due to demonstrated low-period repeated IDs from the randomized IP_id
code. Consensus is that the low-period repetition (much less than
2^15) is not suitable for general-purpose use.
Allocators of new IPv4 IDs should now call the function ip_newid().
Randomized IP_ids is now a config-time option, "options RANDOM_IP_ID".
ip_newid() can use ip_random-id()_IP_ID if and only if configured
with RANDOM_IP_ID. A sysctl knob should be provided.
This API may be reworked in the near future to support linear ip_id
counters per (src,dst) IP-address pair.
configured with ``options FAST_IPSEC''. Kernels with KAME IPsec or
with no IPsec should work as before.
All calls to ip_output() now always pass an additional compulsory
argument: the inpcb associated with the packet being sent,
or 0 if no inpcb is available.
Fast-ipsec tested with ICMP or UDP over ESP. TCP doesn't work, yet.
cegger