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The IRMd will now check the user UID and GID for privileged access,
avoiding unprivileged users being able to disrupt all IPC (e.g. by
shm_open the single pool and corrupting its metadata).
Non-privileged users are now limited to a PUP (per-user pool) for
sending/receiving packets. It is still created by the IRMd, but owned
by the user (uid) with 600 permissions. It does not add additional
copies for local IPC between their own processes (i.e. over the local
IPCP), but packets between processes owned by a different user or
destined over the network (other IPCPs) will incur a copy when
crossing the PUP / PUP or the PUP / GSPP boundary.
Privileged users and users in the ouroboros group still have direct
access to the GSPP (globally shared private pool) for packet transfer
that will avoid additional copies when processing packets between
processes owned by different users and to the network.
This aligns the security model with UNIX trust domains defined by UID
and GID by leveraging file permission on the pools in shared memory.
┌─────────────────────────────────────────────────────────────┐
│ Source Pool │ Dest Pool │ Operation │ Copies │
├─────────────────────────────────────────────────────────────┤
│ GSPP │ GSPP │ Zero-copy │ 0 │
│ PUP.uid │ PUP.uid │ Zero-copy │ 0 │
│ PUP.uid1 │ PUP.uid2 │ memcpy() │ 1 │
│ PUP.uid │ GSPP │ memcpy() │ 1 │
│ GSPP │ PUP.uid │ memcpy() │ 1 │
└─────────────────────────────────────────────────────────────┘
This also renames the struct ai ("application instance") in dev.c to
struct proc (process).
Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>
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This is a first step towards the Secure Shared Memory (SSM)
infrastructure for Ouroboros, which will allow proper resource
separation for non-privileged processes.
This replaces the rdrbuff (random-deletion ring buffer) PoC allocator
with a sharded slab allocator for the packet buffer pool to avoid the
head-of-line blocking behaviour of the rdrb and reduce lock contention
in multi-process scenarios. Each size class contains multiple
independent shards, allowing parallel allocations without blocking.
- Configurable shard count per size class (default: 4, set via
SSM_POOL_SHARDS in CMake). The configured number of blocks are
spread over the number of shards. As an example:
SSM_POOL_512_BLOCKS = 768 blocks total
These 768 blocks are shared among 4 shards
(not 768 × 4 = 3072 blocks)
- Lazy block distribution: all blocks initially reside in shard 0
and naturally migrate to process-local shards upon first
allocation and subsequent free operations
- Fallback with work stealing: processes attempt allocation from
their local shard (pid % SSM_POOL_SHARDS) first, then steal
from other shards if local is exhausted, eliminating
fragmentation while maintaining low contention
- Round-robin condvar signaling: blocking allocations cycle
through all shard condition variables to ensure fairness
- Blocks freed to allocator's shard: uses allocator_pid to
determine target shard, enabling natural load balancing as
process allocation patterns stabilize over time
Maintains existing robust mutex semantics including EOWNERDEAD
handling for dead process recovery. Internal structures exposed in
ssm.h for testing purposes. Adds some tests (pool_test,
pool_sharding_test.c. etc) verifying lazy distribution, migration,
fallback stealing, and multiprocess behavior.
Updates the ring buffer (rbuff) to use relaxed/acquire/release
ordering on atomic indices. The ring buffer requires the (robust)
mutex to ensure cross-structure synchronization between pool buffer
writes and ring buffer index publication.
Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>
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