BSD syscall#512
svc · unix #512
__channel_sync
Synchronizes a Skywalk channel with the kernel, publishing produced slots and reaping completed ones.
Prototype
int __channel_sync(int c, int mode, int flags);Returns: int
Arguments
| Name | Type | Dir | Description |
|---|---|---|---|
| c | int | - | |
| mode | int | - | |
| flags | int | - |
Version history
| XNU tag | macOS | # |
|---|---|---|
| xnu-8792.41.9 | macOS 13.0 Ventura | 512 |
| xnu-10002.1.13 | macOS 14.0 Sonoma | 512 |
| xnu-11215.1.10 | macOS 15.0 Sequoia | 512 |
| xnu-11417.101.15 | macOS 15.4 Sequoia | 512 |
| xnu-12377.1.9 | macOS 26.0 Tahoe | 512 |
| xnu-10002.41.9 | — | 512 |
| xnu-10002.61.3 | — | 512 |
| xnu-10002.81.5 | — | 512 |
| xnu-10063.101.15 | — | 512 |
| xnu-10063.121.3 | — | 512 |
| xnu-10063.141.1 | — | 512 |
| xnu-11215.41.3 | — | 512 |
| xnu-11215.61.5 | — | 512 |
| xnu-11215.81.4 | — | 512 |
| xnu-11417.121.6 | — | 512 |
| xnu-11417.140.69 | — | 512 |
| xnu-12377.101.15 | — | 512 |
| xnu-12377.41.6 | — | 512 |
| xnu-12377.61.12 | — | 512 |
| xnu-12377.81.4 | — | 512 |
| xnu-8019.80.24 | — | 512 |
| xnu-8020.101.4 | — | 512 |
| xnu-8020.121.3 | — | 512 |
| xnu-8020.140.41 | — | 512 |
| xnu-8792.61.2 | — | 512 |
| xnu-8792.81.2 | — | 512 |
| xnu-8796.101.5 | — | 512 |
| xnu-8796.121.2 | — | 512 |
| xnu-8796.141.3 | — | 512 |
Notes
The hot-path syscall of Skywalk: after writing packet metadata into shared-memory rings, user space calls __channel_sync to hand the slots to the nexus, and reads back completion indices for the rx ring. Conceptually similar to Linux's io_uring submit/complete or netmap's NIOCTXSYNC/NIOCRXSYNC. Apple's Network.framework batches dozens of packets per call to amortize the cost.
Detection
Per-packet visibility belongs to the nexus operator (kernel) or to a DriverKit network extension hooked into the same nexus. ES is blind here.
Related APIs
__channel_open__channel_get_infosendmsg_xrecvmsg_x