Re: [PATCH bpf v2] bpf: Update bpf_{g,s}etsockopt() documentation

From: Ji Rongfeng
Date: Tue Nov 29 2022 - 09:17:30 EST


On 2022/11/27 11:27, Ji Rongfeng wrote:
On 2022/11/24 8:40, Martin KaFai Lau wrote:
On 11/23/22 4:18 PM, Daniel Borkmann wrote:
On 11/18/22 9:18 AM, Ji Rongfeng wrote:
* append missing optnames to the end
* simplify bpf_getsockopt()'s doc

Signed-off-by: Ji Rongfeng <SikoJobs@xxxxxxxxxxx>
---
  include/uapi/linux/bpf.h       | 20 ++++++++++++--------
  tools/include/uapi/linux/bpf.h | 20 ++++++++++++--------
  2 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 51b9aa640ad2..14f29d95ea71 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2576,14 +2576,19 @@ union bpf_attr {
   *         * **SOL_SOCKET**, which supports the following *optname*\ s:
   *           **SO_RCVBUF**, **SO_SNDBUF**, **SO_MAX_PACING_RATE**,
   *           **SO_PRIORITY**, **SO_RCVLOWAT**, **SO_MARK**,
- *           **SO_BINDTODEVICE**, **SO_KEEPALIVE**.
+ *           **SO_BINDTODEVICE**, **SO_KEEPALIVE**, **SO_REUSEADDR**,
+ *           **SO_REUSEPORT**, **SO_BINDTOIFINDEX**, **SO_TXREHASH**.
   *         * **IPPROTO_TCP**, which supports the following *optname*\ s:
   *           **TCP_CONGESTION**, **TCP_BPF_IW**,
   *           **TCP_BPF_SNDCWND_CLAMP**, **TCP_SAVE_SYN**,
   *           **TCP_KEEPIDLE**, **TCP_KEEPINTVL**, **TCP_KEEPCNT**,
- *          **TCP_SYNCNT**, **TCP_USER_TIMEOUT**, **TCP_NOTSENT_LOWAT**.
+ *           **TCP_SYNCNT**, **TCP_USER_TIMEOUT**, **TCP_NOTSENT_LOWAT**,
+ *           **TCP_NODELAY**, **TCP_MAXSEG**, **TCP_WINDOW_CLAMP**,
+ *           **TCP_THIN_LINEAR_TIMEOUTS**, **TCP_BPF_DELACK_MAX**,
+ *           **TCP_BPF_RTO_MIN**.
   *         * **IPPROTO_IP**, which supports *optname* **IP_TOS**.
- *         * **IPPROTO_IPV6**, which supports *optname* **IPV6_TCLASS**.
+ *         * **IPPROTO_IPV6**, which supports the following *optname*\ s:
+ *           **IPV6_TCLASS**, **IPV6_AUTOFLOWLABEL**.
   *     Return
   *         0 on success, or a negative error in case of failure.
   *
@@ -2800,12 +2805,11 @@ union bpf_attr {
   *           and **BPF_CGROUP_INET6_CONNECT**.
   *
   *         This helper actually implements a subset of **getsockopt()**.
- *         It supports the following *level*\ s:
+ *         It supports the same set of *optname*\ s that supported by

nit: that is supported by

+ *         **bpf_setsockopt**\ () helper with a few exceptions:
   *
- *         * **IPPROTO_TCP**, which supports *optname*
- *           **TCP_CONGESTION**.
- *         * **IPPROTO_IP**, which supports *optname* **IP_TOS**.
- *         * **IPPROTO_IPV6**, which supports *optname* **IPV6_TCLASS**.
+ *         * **bpf_setsockopt**\ () helper only: **TCP_BPF_***.
+ *         * **bpf_getsockopt**\ () helper only: **TCP_SAVED_SYNC**.

I think from a user PoV the above is a bit hard to follow, maybe take Martin's
earlier feedback into account and add a proper sentence; it will be much easier
to understand.

+1  Made the change and also fixed TCP_SAVED_SYNC with s/SYNC/SYN/ while applying.  Thanks!

Thanks for the helpful reviews. I chose the form of lists was because we could
append more optnames easily in the future. But I believe it's not late to apply
that form when we really need it : )

In my opinion, this patch doesn't contain any new feature, but just a

new features

kind of fix
to the documentation, according to the corresponding code in the bpf tree,
which hasn't been modified yet in the bpf-next tree. So I targeted the former,
as this patch could be useful there. Please let me know if there's any

if there're

customary
rules outside bpf_devel_QA. Thanks!

I just found that SO_BINDTODEVICE is bpf_setsockopt() only. I checked sock_getbindtodevice() and there's nothing special comparing with sock_setbindtodevice(), except "down_read(&devnet_rename_sem);" and "up_read(&devnet_rename_sem);". Martin once wrote:

> The only exception is SO_BINDTODEVICE because it needs to acquire a
> blocking lock. Thus, SO_BINDTODEVICE is not supported.

Were you referring to "down_read(&devnet_rename_sem);"? Seems it's not acquiring a blocking lock. Maybe "devnet_rename_sem" has been locked for writing somewhere in bpf before? Please let me know. Thanks!