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fa046d8774
- The existing ipi_lock continues to protect the global inpcb list and inpcb counter. This lock is now relegated to a small number of allocation and free operations, and occasional operations that walk all connections (including, awkwardly, certain UDP multicast receive operations -- something to revisit). - A new ipi_hash_lock protects the two inpcbinfo hash tables for looking up connections and bound sockets, manipulated using new INP_HASH_*() macros. This lock, combined with inpcb locks, protects the 4-tuple address space. Unlike the current ipi_lock, ipi_hash_lock follows the individual inpcb connection locks, so may be acquired while manipulating a connection on which a lock is already held, avoiding the need to acquire the inpcbinfo lock preemptively when a binding change might later be required. As a result, however, lookup operations necessarily go through a reference acquire while holding the lookup lock, later acquiring an inpcb lock -- if required. A new function in_pcblookup() looks up connections, and accepts flags indicating how to return the inpcb. Due to lock order changes, callers no longer need acquire locks before performing a lookup: the lookup routine will acquire the ipi_hash_lock as needed. In the future, it will also be able to use alternative lookup and locking strategies transparently to callers, such as pcbgroup lookup. New lookup flags are, supplementing the existing INPLOOKUP_WILDCARD flag: INPLOOKUP_RLOCKPCB - Acquire a read lock on the returned inpcb INPLOOKUP_WLOCKPCB - Acquire a write lock on the returned inpcb Callers must pass exactly one of these flags (for the time being). Some notes: - All protocols are updated to work within the new regime; especially, TCP, UDPv4, and UDPv6. pcbinfo ipi_lock acquisitions are largely eliminated, and global hash lock hold times are dramatically reduced compared to previous locking. - The TCP syncache still relies on the pcbinfo lock, something that we may want to revisit. - Support for reverting to the FreeBSD 7.x locking strategy in TCP input is no longer available -- hash lookup locks are now held only very briefly during inpcb lookup, rather than for potentially extended periods. However, the pcbinfo ipi_lock will still be acquired if a connection state might change such that a connection is added or removed. - Raw IP sockets continue to use the pcbinfo ipi_lock for protection, due to maintaining their own hash tables. - The interface in6_pcblookup_hash_locked() is maintained, which allows callers to acquire hash locks and perform one or more lookups atomically with 4-tuple allocation: this is required only for TCPv6, as there is no in6_pcbconnect_setup(), which there should be. - UDPv6 locking remains significantly more conservative than UDPv4 locking, which relates to source address selection. This needs attention, as it likely significantly reduces parallelism in this code for multithreaded socket use (such as in BIND). - In the UDPv4 and UDPv6 multicast cases, we need to revisit locking somewhat, as they relied on ipi_lock to stablise 4-tuple matches, which is no longer sufficient. A second check once the inpcb lock is held should do the trick, keeping the general case from requiring the inpcb lock for every inpcb visited. - This work reminds us that we need to revisit locking of the v4/v6 flags, which may be accessed lock-free both before and after this change. - Right now, a single lock name is used for the pcbhash lock -- this is undesirable, and probably another argument is required to take care of this (or a char array name field in the pcbinfo?). This is not an MFC candidate for 8.x due to its impact on lookup and locking semantics. It's possible some of these issues could be worked around with compatibility wrappers, if necessary. Reviewed by: bz Sponsored by: Juniper Networks, Inc. |
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| .. | ||
| dest6.c | ||
| frag6.c | ||
| icmp6.c | ||
| icmp6.h | ||
| in6.c | ||
| in6.h | ||
| in6_cksum.c | ||
| in6_gif.c | ||
| in6_gif.h | ||
| in6_ifattach.c | ||
| in6_ifattach.h | ||
| in6_mcast.c | ||
| in6_pcb.c | ||
| in6_pcb.h | ||
| in6_proto.c | ||
| in6_rmx.c | ||
| in6_src.c | ||
| in6_var.h | ||
| ip6.h | ||
| ip6_ecn.h | ||
| ip6_forward.c | ||
| ip6_id.c | ||
| ip6_input.c | ||
| ip6_ipsec.c | ||
| ip6_ipsec.h | ||
| ip6_mroute.c | ||
| ip6_mroute.h | ||
| ip6_output.c | ||
| ip6_var.h | ||
| ip6protosw.h | ||
| mld6.c | ||
| mld6.h | ||
| mld6_var.h | ||
| nd6.c | ||
| nd6.h | ||
| nd6_nbr.c | ||
| nd6_rtr.c | ||
| pim6.h | ||
| pim6_var.h | ||
| raw_ip6.c | ||
| raw_ip6.h | ||
| route6.c | ||
| scope6.c | ||
| scope6_var.h | ||
| sctp6_usrreq.c | ||
| sctp6_var.h | ||
| send.c | ||
| send.h | ||
| tcp6_var.h | ||
| udp6_usrreq.c | ||
| udp6_var.h | ||