The extended Berkeley Packet Filter (eBPF) subsystem consists in programs
written in a pseudo\-assembly language, then attached to one of the several
kernel hooks and run in reaction of specific events. This framework differs
-from the older, \(dqclassic\(dq BPF (or \(dqcBPF\(dq) in several aspects, one of them being
-the ability to call special functions (or \(dqhelpers\(dq) from within a program.
+from the older, \[dq]classic\[dq] BPF (or \[dq]cBPF\[dq]) in several aspects, one of them being
+the ability to call special functions (or \[dq]helpers\[dq]) from within a program.
These functions are restricted to a white\-list of helpers defined in the
kernel.
.sp
.INDENT 7.0
.TP
.B Description
-This helper is a \(dqprintk()\-like\(dq facility for debugging. It
+This helper is a \[dq]printk()\-like\[dq] facility for debugging. It
prints a message defined by format \fIfmt\fP (of size \fIfmt_size\fP)
to file \fI/sys/kernel/debug/tracing/trace\fP from DebugFS, if
available. It can take up to three additional \fBu64\fP
Also, note that \fBbpf_trace_printk\fP() is slow, and should
only be used for debugging purposes. For this reason, a notice
block (spanning several lines) is printed to kernel logs and
-states that the helper should not be used \(dqfor production use\(dq
+states that the helper should not be used \[dq]for production use\[dq]
the first time this helper is used (or more precisely, when
\fBtrace_printk\fP() buffers are allocated). For passing values
to user space, perf events should be preferred.
.INDENT 7.0
.TP
.B Description
-This special helper is used to trigger a \(dqtail call\(dq, or in
+This special helper is used to trigger a \[dq]tail call\[dq], or in
other words, to jump into another eBPF program. The same stack
frame is used (but values on stack and in registers for the
caller are not accessible to the callee). This mechanism allows
.sp
This helper is only available is the kernel was compiled with
the \fBCONFIG_CGROUP_NET_CLASSID\fP configuration option set to
-\(dq\fBy\fP\(dq or to \(dq\fBm\fP\(dq.
+\[dq]\fBy\fP\[dq] or to \[dq]\fBm\fP\[dq].
.TP
.B Return
The classid, or 0 for the default unconfigured classid.
principal parameters used by various tunneling protocols into a
single struct. This way, it can be used to easily make a
decision based on the contents of the encapsulation header,
-\(dqsummarized\(dq in this struct. In particular, it holds the IP
+\[dq]summarized\[dq] in this struct. In particular, it holds the IP
address of the remote end (IPv4 or IPv6, depending on the case)
in \fIkey\fP\fB\->remote_ipv4\fP or \fIkey\fP\fB\->remote_ipv6\fP\&. Also,
this struct exposes the \fIkey\fP\fB\->tunnel_id\fP, which is
.UNINDENT
.sp
This interface can also be used with all encapsulation devices
-that can operate in \(dqcollect metadata\(dq mode: instead of having
-one network device per specific configuration, the \(dqcollect
-metadata\(dq mode only requires a single device where the
+that can operate in \[dq]collect metadata\[dq] mode: instead of having
+one network device per specific configuration, the \[dq]collect
+metadata\[dq] mode only requires a single device where the
configuration can be extracted from this helper.
.sp
This can be used together with various tunnels such as VXLan,
\fIto\fP\&.
.sp
Since Linux 4.7, usage of this helper has mostly been replaced
-by \(dqdirect packet access\(dq, enabling packet data to be
+by \[dq]direct packet access\[dq], enabling packet data to be
manipulated with \fIskb\fP\fB\->data\fP and \fIskb\fP\fB\->data_end\fP
pointing respectively to the first byte of packet data and to
the byte after the last byte of packet data. However, it
of \fIsize\fP\&.
.sp
This helper can be used with encapsulation devices that can
-operate in \(dqcollect metadata\(dq mode (please refer to the related
+operate in \[dq]collect metadata\[dq] mode (please refer to the related
note in the description of \fBbpf_skb_get_tunnel_key\fP() for
more details). A particular example where this can be used is
in combination with the Geneve encapsulation protocol, where it
.TP
.B Description
Retrieve the XFRM state (IP transform framework, see also
-\fBip\-xfrm(8)\fP) at \fIindex\fP in XFRM \(dqsecurity path\(dq for \fIskb\fP\&.
+\fBip\-xfrm(8)\fP) at \fIindex\fP in XFRM \[dq]security path\[dq] for \fIskb\fP\&.
.sp
The retrieved value is stored in the \fBstruct bpf_xfrm_state\fP
pointed by \fIxfrm_state\fP and of length \fIsize\fP\&.
Base offset to load data from is \fIskb\fP\[aq]s network header.
.UNINDENT
.sp
-In general, \(dqdirect packet access\(dq is the preferred method to
+In general, \[dq]direct packet access\[dq] is the preferred method to
access packet data, however, this helper is in particular useful
in socket filters where \fIskb\fP\fB\->data\fP does not always point
-to the start of the mac header and where \(dqdirect packet access\(dq
+to the start of the mac header and where \[dq]direct packet access\[dq]
is not available.
.TP
.B Return
.sp
This helper is only available is the kernel was compiled with
the \fBCONFIG_BPF_LIRC_MODE2\fP configuration option set to
-\(dq\fBy\fP\(dq.
+\[dq]\fBy\fP\[dq].
.TP
.B Return
0
.sp
This helper is only available is the kernel was compiled with
the \fBCONFIG_BPF_LIRC_MODE2\fP configuration option set to
-\(dq\fBy\fP\(dq.
+\[dq]\fBy\fP\[dq].
.TP
.B Return
0
.sp
This helper is only available is the kernel was compiled with
the \fBCONFIG_BPF_LIRC_MODE2\fP configuration option set to
-\(dq\fBy\fP\(dq.
+\[dq]\fBy\fP\[dq].
.TP
.B Return
0
.sp
The buffer is always NUL terminated, unless it\[aq]s zero\-sized.
.sp
-If \fIflags\fP is zero, full name (e.g. \(dqnet/ipv4/tcp_mem\(dq) is
+If \fIflags\fP is zero, full name (e.g. \[dq]net/ipv4/tcp_mem\[dq]) is
copied. Use \fBBPF_F_SYSCTL_BASE_NAME\fP flag to copy base name
-only (e.g. \(dqtcp_mem\(dq).
+only (e.g. \[dq]tcp_mem\[dq]).
.TP
.B Return
Number of character copied (not including the trailing NUL).
.sp
Underneath, the value is stored locally at \fIsk\fP instead of
the \fImap\fP\&. The \fImap\fP is used as the bpf\-local\-storage
-\(dqtype\(dq. The bpf\-local\-storage \(dqtype\(dq (i.e. the \fImap\fP) is
+\[dq]type\[dq]. The bpf\-local\-storage \[dq]type\[dq] (i.e. the \fImap\fP) is
searched against all bpf\-local\-storages residing at \fIsk\fP\&.
.sp
\fIsk\fP is a kernel \fBstruct sock\fP pointer for LSM program.
.sp
.nf
.ft C
-SEC(\(dqkprobe/sys_open\(dq)
+SEC(\[dq]kprobe/sys_open\[dq])
void bpf_sys_open(struct pt_regs *ctx)
{
char buf[PATHLEN]; // PATHLEN is defined to 256
.sp
If the searching kind is an experimental kind
(i.e. 253 or 254 according to RFC6994). It also
-needs to specify the \(dqmagic\(dq which is either
+needs to specify the \[dq]magic\[dq] which is either
2 bytes or 4 bytes. It then also needs to
specify the size of the magic by using
-the 2nd byte which is \(dqkind\-length\(dq of a TCP
-header option and the \(dqkind\-length\(dq also
-includes the first 2 bytes \(dqkind\(dq and \(dqkind\-length\(dq
+the 2nd byte which is \[dq]kind\-length\[dq] of a TCP
+header option and the \[dq]kind\-length\[dq] also
+includes the first 2 bytes \[dq]kind\[dq] and \[dq]kind\-length\[dq]
itself as a normal TCP header option also does.
.sp
For example, to search experimental kind 254 with
.sp
Underneath, the value is stored locally at \fIinode\fP instead of
the \fImap\fP\&. The \fImap\fP is used as the bpf\-local\-storage
-\(dqtype\(dq. The bpf\-local\-storage \(dqtype\(dq (i.e. the \fImap\fP) is
+\[dq]type\[dq]. The bpf\-local\-storage \[dq]type\[dq] (i.e. the \fImap\fP) is
searched against all bpf_local_storage residing at \fIinode\fP\&.
.sp
An optional \fIflags\fP (\fBBPF_LOCAL_STORAGE_GET_F_CREATE\fP) can be
.sp
Underneath, the value is stored locally at \fItask\fP instead of
the \fImap\fP\&. The \fImap\fP is used as the bpf\-local\-storage
-\(dqtype\(dq. The bpf\-local\-storage \(dqtype\(dq (i.e. the \fImap\fP) is
+\[dq]type\[dq]. The bpf\-local\-storage \[dq]type\[dq] (i.e. the \fImap\fP) is
searched against all bpf_local_storage residing at \fItask\fP\&.
.sp
An optional \fIflags\fP (\fBBPF_LOCAL_STORAGE_GET_F_CREATE\fP) can be
.INDENT 7.0
.TP
.B Description
-Return a BTF pointer to the \(dqcurrent\(dq task.
+Return a BTF pointer to the \[dq]current\[dq] task.
This pointer can also be used in helpers that accept an
\fIARG_PTR_TO_BTF_ID\fP of type \fItask_struct\fP\&.
.TP
eBPF programs can have an associated license, passed along with the bytecode
instructions to the kernel when the programs are loaded. The format for that
string is identical to the one in use for kernel modules (Dual licenses, such
-as \(dqDual BSD/GPL\(dq, may be used). Some helper functions are only accessible to
+as \[dq]Dual BSD/GPL\[dq], may be used). Some helper functions are only accessible to
programs that are compatible with the GNU Privacy License (GPL).
.sp
In order to use such helpers, the eBPF program must be loaded with the correct
.sp
.nf
.ft C
-char ____license[] __attribute__((section(\(dqlicense\(dq), used)) = \(dqGPL\(dq;
+char ____license[] __attribute__((section(\[dq]license\[dq]), used)) = \[dq]GPL\[dq];
.ft P
.fi
.UNINDENT
projects / thirdparty / man-pages.git / commitdiff
