4 files changed, 138 insertions, 9 deletions
diff --git a/Documentation/bpf/bpf_devel_QA.rst b/Documentation/bpf/bpf_devel_QA.rst
index a26aa1b9b259..5b613d2a5f1a 100644
--- a/Documentation/bpf/bpf_devel_QA.rst
+++ b/Documentation/bpf/bpf_devel_QA.rst
@@ -60,13 +60,13 @@ Q: Where can I find patches currently under discussion for BPF subsystem?
 A: All patches that are Cc'ed to netdev are queued for review under netdev
 patchwork project:
 
-  http://patchwork.ozlabs.org/project/netdev/list/
+  https://patchwork.kernel.org/project/netdevbpf/list/
 
 Those patches which target BPF, are assigned to a 'bpf' delegate for
 further processing from BPF maintainers. The current queue with
 patches under review can be found at:
 
-  https://patchwork.ozlabs.org/project/netdev/list/?delegate=77147
+  https://patchwork.kernel.org/project/netdevbpf/list/?delegate=121173
 
 Once the patches have been reviewed by the BPF community as a whole
 and approved by the BPF maintainers, their status in patchwork will be
@@ -149,7 +149,7 @@ In case the patch or patch series has to be reworked and sent out
 again in a second or later revision, it is also required to add a
 version number (``v2``, ``v3``, ...) into the subject prefix::
 
-  git format-patch --subject-prefix='PATCH net-next v2' start..finish
+  git format-patch --subject-prefix='PATCH bpf-next v2' start..finish
 
 When changes have been requested to the patch series, always send the
 whole patch series again with the feedback incorporated (never send
@@ -479,17 +479,18 @@ LLVM's static compiler lists the supported targets through
 
      $ llc --version
      LLVM (http://llvm.org/):
-       LLVM version 6.0.0svn
+       LLVM version 10.0.0
        Optimized build.
        Default target: x86_64-unknown-linux-gnu
        Host CPU: skylake
 
        Registered Targets:
-         bpf    - BPF (host endian)
-         bpfeb  - BPF (big endian)
-         bpfel  - BPF (little endian)
-         x86    - 32-bit X86: Pentium-Pro and above
-         x86-64 - 64-bit X86: EM64T and AMD64
+         aarch64    - AArch64 (little endian)
+         bpf        - BPF (host endian)
+         bpfeb      - BPF (big endian)
+         bpfel      - BPF (little endian)
+         x86        - 32-bit X86: Pentium-Pro and above
+         x86-64     - 64-bit X86: EM64T and AMD64
 
 For developers in order to utilize the latest features added to LLVM's
 BPF back end, it is advisable to run the latest LLVM releases. Support
@@ -517,6 +518,10 @@ from the git repositories::
 The built binaries can then be found in the build/bin/ directory, where
 you can point the PATH variable to.
 
+Set ``-DLLVM_TARGETS_TO_BUILD`` equal to the target you wish to build, you
+will find a full list of targets within the llvm-project/llvm/lib/Target
+directory.
+
 Q: Reporting LLVM BPF issues
 ----------------------------
 Q: Should I notify BPF kernel maintainers about issues in LLVM's BPF code
diff --git a/Documentation/bpf/btf.rst b/Documentation/bpf/btf.rst
index b5361b8621c9..44dc789de2b4 100644
--- a/Documentation/bpf/btf.rst
+++ b/Documentation/bpf/btf.rst
@@ -724,6 +724,31 @@ want to define unused entry in BTF_ID_LIST, like::
       BTF_ID_UNUSED
       BTF_ID(struct, task_struct)
 
+The ``BTF_SET_START/END`` macros pair defines sorted list of BTF ID values
+and their count, with following syntax::
+
+  BTF_SET_START(set)
+  BTF_ID(type1, name1)
+  BTF_ID(type2, name2)
+  BTF_SET_END(set)
+
+resulting in following layout in .BTF_ids section::
+
+  __BTF_ID__set__set:
+  .zero 4
+  __BTF_ID__type1__name1__3:
+  .zero 4
+  __BTF_ID__type2__name2__4:
+  .zero 4
+
+The ``struct btf_id_set set;`` variable is defined to access the list.
+
+The ``typeX`` name can be one of following::
+
+   struct, union, typedef, func
+
+and is used as a filter when resolving the BTF ID value.
+
 All the BTF ID lists and sets are compiled in the .BTF_ids section and
 resolved during the linking phase of kernel build by ``resolve_btfids`` tool.
 
diff --git a/Documentation/bpf/index.rst b/Documentation/bpf/index.rst
index 7df2465fd108..4f2874b729c3 100644
--- a/Documentation/bpf/index.rst
+++ b/Documentation/bpf/index.rst
@@ -52,6 +52,7 @@ Program types
    prog_cgroup_sysctl
    prog_flow_dissector
    bpf_lsm
+   prog_sk_lookup
 
 
 Map types
diff --git a/Documentation/bpf/prog_sk_lookup.rst b/Documentation/bpf/prog_sk_lookup.rst
new file mode 100644
index 000000000000..85a305c19bcd
--- /dev/null
+++ b/Documentation/bpf/prog_sk_lookup.rst
@@ -0,0 +1,98 @@
+.. SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+
+=====================
+BPF sk_lookup program
+=====================
+
+BPF sk_lookup program type (``BPF_PROG_TYPE_SK_LOOKUP``) introduces programmability
+into the socket lookup performed by the transport layer when a packet is to be
+delivered locally.
+
+When invoked BPF sk_lookup program can select a socket that will receive the
+incoming packet by calling the ``bpf_sk_assign()`` BPF helper function.
+
+Hooks for a common attach point (``BPF_SK_LOOKUP``) exist for both TCP and UDP.
+
+Motivation
+==========
+
+BPF sk_lookup program type was introduced to address setup scenarios where
+binding sockets to an address with ``bind()`` socket call is impractical, such
+as:
+
+1. receiving connections on a range of IP addresses, e.g. 192.0.2.0/24, when
+   binding to a wildcard address ``INADRR_ANY`` is not possible due to a port
+   conflict,
+2. receiving connections on all or a wide range of ports, i.e. an L7 proxy use
+   case.
+
+Such setups would require creating and ``bind()``'ing one socket to each of the
+IP address/port in the range, leading to resource consumption and potential
+latency spikes during socket lookup.
+
+Attachment
+==========
+
+BPF sk_lookup program can be attached to a network namespace with
+``bpf(BPF_LINK_CREATE, ...)`` syscall using the ``BPF_SK_LOOKUP`` attach type and a
+netns FD as attachment ``target_fd``.
+
+Multiple programs can be attached to one network namespace. Programs will be
+invoked in the same order as they were attached.
+
+Hooks
+=====
+
+The attached BPF sk_lookup programs run whenever the transport layer needs to
+find a listening (TCP) or an unconnected (UDP) socket for an incoming packet.
+
+Incoming traffic to established (TCP) and connected (UDP) sockets is delivered
+as usual without triggering the BPF sk_lookup hook.
+
+The attached BPF programs must return with either ``SK_PASS`` or ``SK_DROP``
+verdict code. As for other BPF program types that are network filters,
+``SK_PASS`` signifies that the socket lookup should continue on to regular
+hashtable-based lookup, while ``SK_DROP`` causes the transport layer to drop the
+packet.
+
+A BPF sk_lookup program can also select a socket to receive the packet by
+calling ``bpf_sk_assign()`` BPF helper. Typically, the program looks up a socket
+in a map holding sockets, such as ``SOCKMAP`` or ``SOCKHASH``, and passes a
+``struct bpf_sock *`` to ``bpf_sk_assign()`` helper to record the
+selection. Selecting a socket only takes effect if the program has terminated
+with ``SK_PASS`` code.
+
+When multiple programs are attached, the end result is determined from return
+codes of all the programs according to the following rules:
+
+1. If any program returned ``SK_PASS`` and selected a valid socket, the socket
+   is used as the result of the socket lookup.
+2. If more than one program returned ``SK_PASS`` and selected a socket, the last
+   selection takes effect.
+3. If any program returned ``SK_DROP``, and no program returned ``SK_PASS`` and
+   selected a socket, socket lookup fails.
+4. If all programs returned ``SK_PASS`` and none of them selected a socket,
+   socket lookup continues on.
+
+API
+===
+
+In its context, an instance of ``struct bpf_sk_lookup``, BPF sk_lookup program
+receives information about the packet that triggered the socket lookup. Namely:
+
+* IP version (``AF_INET`` or ``AF_INET6``),
+* L4 protocol identifier (``IPPROTO_TCP`` or ``IPPROTO_UDP``),
+* source and destination IP address,
+* source and destination L4 port,
+* the socket that has been selected with ``bpf_sk_assign()``.
+
+Refer to ``struct bpf_sk_lookup`` declaration in ``linux/bpf.h`` user API
+header, and `bpf-helpers(7)
+<https://man7.org/linux/man-pages/man7/bpf-helpers.7.html>`_ man-page section
+for ``bpf_sk_assign()`` for details.
+
+Example
+=======
+
+See ``tools/testing/selftests/bpf/prog_tests/sk_lookup.c`` for the reference
+implementation.