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29363fb4 |
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23-Nov-2023 |
Warner Losh <imp@FreeBSD.org> |
sys: Remove ancient SCCS tags. Remove ancient SCCS tags from the tree, automated scripting, with two minor fixup to keep things compiling. All the common forms in the tree were removed with a perl script. Sponsored by: Netflix
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7b92493a |
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20-Apr-2023 |
Mark Johnston <markj@FreeBSD.org> |
inpcb: Avoid inp_cred dereferences in SMR-protected lookup The SMR-protected inpcb lookup algorithm currently has to check whether a matching inpcb belongs to a jail, in order to prioritize jailed bound sockets. To do this it has to maintain a ucred reference, and for this to be safe, the reference can't be released until the UMA destructor is called, and this will not happen within any bounded time period. Changing SMR to periodically recycle garbage is not trivial. Instead, let's implement SMR-synchronized lookup without needing to dereference inp_cred. This will allow the inpcb code to free the inp_cred reference immediately when a PCB is freed, ensuring that ucred (and thus jail) references are released promptly. Commit 220d89212943 ("inpcb: immediately return matching pcb on lookup") gets us part of the way there. This patch goes further to handle lookups of unconnected sockets. Here, the strategy is to maintain a well-defined order of items within a hash chain so that a wild lookup can simply return the first match and preserve existing semantics. This makes insertion of listening sockets more complicated in order to make lookup simpler, which seems like the right tradeoff anyway given that bind() is already a fairly expensive operation and lookups are more common. In particular, when inserting an unconnected socket, in_pcbinhash() now keeps the following ordering: - jailed sockets before non-jailed sockets, - specified local addresses before unspecified local addresses. Most of the change adds a separate SMR-based lookup path for inpcb hash lookups. When a match is found, we try to lock the inpcb and re-validate its connection info. In the common case, this works well and we can simply return the inpcb. If this fails, typically because something is concurrently modifying the inpcb, we go to the slow path, which performs a serialized lookup. Note, I did not touch lbgroup lookup, since there the credential reference is formally synchronized by net_epoch, not SMR. In particular, lbgroups are rarely allocated or freed. I think it is possible to simplify in_pcblookup_hash_wild_locked() now, but I didn't do it in this patch. Discussed with: glebius Tested by: glebius Sponsored by: Klara, Inc. Sponsored by: Modirum MDPay Differential Revision: https://reviews.freebsd.org/D38572
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a0577692 |
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26-Dec-2021 |
Gleb Smirnoff <glebius@FreeBSD.org> |
in_pcb: use jenkins hash over the entire IPv6 (or IPv4) address The intent is to provide more entropy than can be provided by just the 32-bits of the IPv6 address which overlaps with 6to4 tunnels. This is needed to mitigate potential algorithmic complexity attacks from attackers who can control large numbers of IPv6 addresses. Together with: gallatin Reviewed by: dwmalone, rscheff Differential revision: https://reviews.freebsd.org/D33254
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de2d4784 |
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02-Dec-2021 |
Gleb Smirnoff <glebius@FreeBSD.org> |
SMR protection for inpcbs With introduction of epoch(9) synchronization to network stack the inpcb database became protected by the network epoch together with static network data (interfaces, addresses, etc). However, inpcb aren't static in nature, they are created and destroyed all the time, which creates some traffic on the epoch(9) garbage collector. Fairly new feature of uma(9) - Safe Memory Reclamation allows to safely free memory in page-sized batches, with virtually zero overhead compared to uma_zfree(). However, unlike epoch(9), it puts stricter requirement on the access to the protected memory, needing the critical(9) section to access it. Details: - The database is already build on CK lists, thanks to epoch(9). - For write access nothing is changed. - For a lookup in the database SMR section is now required. Once the desired inpcb is found we need to transition from SMR section to r/w lock on the inpcb itself, with a check that inpcb isn't yet freed. This requires some compexity, since SMR section itself is a critical(9) section. The complexity is hidden from KPI users in inp_smr_lock(). - For a inpcb list traversal (a pcblist sysctl, or broadcast notification) also a new KPI is provided, that hides internals of the database - inp_next(struct inp_iterator *). Reviewed by: rrs Differential revision: https://reviews.freebsd.org/D33022
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