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All the mediums we have implemented know their minimum
transmit unit. The minimum transfer unit is not adjustable
so there is no point in caching it in the ip interface.
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Wlock()'ing the ifc causes a deadlock with Medium
bind/unbind as the routine can walk /net, while
ndb/dns or ndb/cs are currently blocked enumerating
/net/ipifc/*.
The fix is to have a fake medium, called "unbound",
that is set temporarily during the call of Medium
bind and unbind.
That way, the interface rwlock can be released while
bind/unbind is in progress.
The ipifcunbind() routine will refuse to unbind a
ifc that is currently assigned to the "unbound"
medium, preventing any accidents.
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Instead of having to do an arp hash table lookup for each
outgoing ip packet, forward the Routehint pointer to the
medium's bwrite() function and let it cache the arp entry
pointer.
This avoids route and arp hash table lookups for tcp, il
and connection oriented udp.
It also allows us to avoid multiple route and arp table
lookups for the retransmits once an arp/neighbour solicitation
response arrives.
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The IPv4 ARP cache used to indefinitely buffer packets in the Arpent hold list.
This is bad in case of a router, because it opens a 1 second
(retransmit time) window to leak all the to be forwarded packets.
This change makes the ipv4 arp code path similar to the IPv6 neighbour
solicitation path, using the retransmit process to time out old entries
(after 3 arp retransmits => 3 seconds).
A new function arpcontinue() has been added that unifies the point when
we schedule the (ipv6 sol retransmit) / (ipv4 arp timeout) and reduce
the hold queue to the last packet and unlock the cache.
As a bonus, we also now send a icmp host unreachable notification
for the dropped packets.
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to prevent deadlock on media unbind (which is called with
the interface wlock()'ed), the medias reader processes
that unbind was waiting for used to discard packets when
the interface could not be rlocked.
this has the unfortunate side effect that when we change
addresses on a interface that packets are getting lost.
this is problematic for the processing of ipv6 router
advertisements when multiple RA's are getting received
in quick succession.
this change removes that packet dropping behaviour and
instead changes the unbind process to avoid the deadlock
by wunlock()ing the interface temporarily while waiting
for the reader processes to finish. the interface media
is also changed to the mullmedium before unlocking (see
the comment).
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when making outgoing connections, the source ip was selected
by just iterating from the first to the last interface and
trying each local address until a route was found. the result
was kind of hard to predict as it depends on the interface
order.
this change replaces the algorithm with the route lookup algorithm
that we already have which takes more specific desination and
source prefixes into account. so the order of interfaces does
not matter anymore.
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mark reader process pointers with (void*)-1 to mean
not started yet. this avoids the race condition when
media unbind happens before the kproc has set its
Proc* pointer. then we would not post the note and
the reader would continue running after unbind.
etherbind can be simplified by reading the #lX/addr
file to get the mac address, avoiding the temporary
buffer.
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sending multicast was broken when ipconfig assigned the 0
address for dhcp as they would wrongly classified as Runi.
this could happen when we do slaac and dhcp in parallel,
breaking the sending of router solicitations.
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during dhcp, ipconfig assigns the null address :: which makes
ipforme() return Runi for any destination, which can trigger
arp resolution when we attempt to reply. so have v4local()
skip the null address and have sendarp() check the return
status of v4local(), avoing the spurious arp requests.
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there appears to be confusion about the refresh flag of arpenter().
when we get an arp reply, it makes more sense to just refresh
waiting/existing entries instead creating a new one as we do not
know if we are going to communicate with the remote host in the future.
when we see an arp request for ourselfs however, we want to always
enter the senders address into the arp cache as it is likely the sender
attempts to communicate with us and with the arp entry, we can reply
immidiately.
reject senders from multicast/broadcast mac addresses. thats just silly.
we can get rid of the multicast/broadcast ip checks in ethermedium and
do it in arpenter() instead, checking the route type for the target to
see if its a non unicast target.
enforce strict separation of interface's arp entries by passing a
rlock'd ifc explicitely to arpenter, which we compare against the route
target interface. this makes sure arp/ndp replies only affect entries for
the receiving interface.
handle neighbor solicitation retransmission in nbsendsol() only. that is,
both ethermedium and the rxmitproc just call nbsendsol() which maintains
the timers and counters and handles the rotation on the re-transmission
chain.
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remove tentative check
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cleanup
rfc4861 7.2.2:
If the source address of the packet prompting the solicitation is the
same as one of the addresses assigned to the outgoing interface, that
address SHOULD be placed in the IP Source Address of the outgoing
solicitation.
this change adds ndbsendsol() which handles the source address selection
and also handles the arp table locking; avoiding access to the arp entry
after the arp table is unlocked.
cleanups:
- use ipmove() instead of memmove().
- useless extern qualifiers
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ipv4local() and ipv6local() now take remote address argument,
returning the closest local address to the source. this
implements the standartized source address selection rules
instead of just returning the first local v4 or v6 address.
the source address selection was broken for esp, rudp an udp,
blindly assuming ifc->lifc->local being a valid v4 address.
use ipv6local() instead.
the v6 routing code used to lookup source address route to
decide to drop the packet instead of checking the interface
on the destination route.
factor out the route hint from Conv and put it in Routehint
structure. avoiding stack bloat in v4 routing. implement the
same trick for v6 avoiding second route lookup in ipoput6.
fix memory leak in icmpv6 router solicitation handling.
remove old unfinished handling of multiple v6 routers. should
implement source specific routes instead.
avoid duplication, use common convipvers() function.
use isv4() instead of memcmp v4prefix.
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in Dev.bwrite()
the convention for Dev.bwrite() is that it accepts a *single* block,
and not a block chain. so we never have concatblock here.
to keep stuff consistent, we also guarantee thet Medium.bwrite()
will get a *single* block passed as well, as the callers are
few in number.
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on usb ethernet, it can happen that we read truncated packets smaller
than the ethernet header size. this produces a warning in pullupblock()
later like: "pullup negative length packet, called from 0xf0199e46"
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