mirror of
https://github.com/opnsense/src.git
synced 2026-03-26 20:53:08 -04:00
ce12afaa6f
In emulated mode, the FreeBSD netmap port attempts to perform zero-copy transmission. This works as follows: the kernel ring is populated with mbuf headers to which netmap buffers are attached. When transmitting, the mbuf refcount is initialized to 2, and when the counter value has been decremented to 1 netmap infers that the driver has freed the mbuf and thus transmission is complete. This scheme does not generalize to the situation where netmap is attaching to a software interface which may transmit packets among multiple "queues", as is the case with bridge or lagg interfaces. In that case, we would be relying on backing hardware drivers to free transmitted mbufs promptly, but this isn't guaranteed; a driver may reasonably defer freeing a small number of transmitted buffers indefinitely. If such a buffer ends up at the tail of a netmap transmit ring, further transmits can end up blocked indefinitely. Fix the problem by removing the zero-copy scheme (which is also not implemented in the Linux port of netmap). Instead, the kernel ring is populated with regular mbuf clusters into which netmap buffers are copied by nm_os_generic_xmit_frame(). The refcounting scheme is preserved, and this lets us avoid allocating a fresh cluster per transmitted packet in the common case. If the transmit ring is full, a callout is used to free the "stuck" mbuf, avoiding the queue deadlock described above. Furthermore, when recycling mbuf clusters, be sure to fully reinitialize the mbuf header instead of simply re-setting M_PKTHDR. Some software interfaces, like if_vlan, may set fields in the header which should be reset before the mbuf is reused. Reviewed by: vmaffione MFC after: 1 month Sponsored by: Zenarmor Sponsored by: OPNsense Sponsored by: Klara, Inc. Differential Revision: https://reviews.freebsd.org/D38065 |
||
|---|---|---|
| .. | ||
| amd64 | ||
| arm | ||
| arm64 | ||
| bsm | ||
| cam | ||
| cddl | ||
| compat | ||
| conf | ||
| contrib | ||
| crypto | ||
| ddb | ||
| dev | ||
| dts | ||
| fs | ||
| gdb | ||
| geom | ||
| gnu | ||
| i386 | ||
| isa | ||
| kern | ||
| kgssapi | ||
| libkern | ||
| modules | ||
| net | ||
| net80211 | ||
| netgraph | ||
| netinet | ||
| netinet6 | ||
| netipsec | ||
| netlink | ||
| netpfil | ||
| netsmb | ||
| nfs | ||
| nfsclient | ||
| nfsserver | ||
| nlm | ||
| ofed | ||
| opencrypto | ||
| powerpc | ||
| riscv | ||
| rpc | ||
| security | ||
| sys | ||
| teken | ||
| tests | ||
| tools | ||
| ufs | ||
| vm | ||
| x86 | ||
| xdr | ||
| xen | ||
| Makefile | ||
| README.md | ||
FreeBSD Kernel Source:
This directory contains the source files and build glue that make up the FreeBSD kernel and its modules, including both original and contributed software.
Kernel configuration files are located in the conf/ subdirectory of each
architecture. GENERIC is the configuration used in release builds. NOTES
contains documentation of all possible entries. LINT is a compile-only
configuration used to maximize build coverage and detect regressions.
Source Roadmap:
| Directory | Description |
|---|---|
| amd64 | AMD64 (64-bit x86) architecture support |
| arm | 32-bit ARM architecture support |
| arm64 | 64-bit ARM (AArch64) architecture support |
| cam | Common Access Method storage subsystem - cam(4) and ctl(4) |
| cddl | CDDL-licensed optional sources such as DTrace |
| conf | kernel build glue |
| compat | Linux compatibility layer, FreeBSD 32-bit compatibility |
| contrib | 3rd-party imported software such as OpenZFS |
| crypto | crypto drivers |
| ddb | interactive kernel debugger - ddb(4) |
| fs | most filesystems, excluding UFS, NFS, and ZFS |
| dev | device drivers and other arch independent code |
| gdb | kernel remote GDB stub - gdb(4) |
| geom | GEOM framework - geom(4) |
| i386 | i386 (32-bit x86) architecture support |
| kern | main part of the kernel |
| libkern | libc-like and other support functions for kernel use |
| modules | kernel module infrastructure |
| net | core networking code |
| net80211 | wireless networking (IEEE 802.11) - net80211(4) |
| netgraph | graph-based networking subsystem - netgraph(4) |
| netinet | IPv4 protocol implementation - inet(4) |
| netinet6 | IPv6 protocol implementation - inet6(4) |
| netipsec | IPsec protocol implementation - ipsec(4) |
| netpfil | packet filters - ipfw(4), pf(4), and ipfilter(4) |
| opencrypto | OpenCrypto framework - crypto(7) |
| powerpc | PowerPC/POWER (32 and 64-bit) architecture support |
| riscv | 64-bit RISC-V architecture support |
| security | security facilities - audit(4) and mac(4) |
| sys | kernel headers |
| tests | kernel unit tests |
| ufs | Unix File System - ffs(7) |
| vm | virtual memory system |
| x86 | code shared by AMD64 and i386 architectures |