| Message ID | 20210401155704.35341-1-otto.hollmann@suse.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | a7a80b17c750c0f4b2c15cc61be5ff7c1d29f8d6 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net-next] net: document a side effect of ip_local_reserved_ports | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for net-next |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | warning | 1 maintainers not CCed: linux-doc@vger.kernel.org |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 10 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
Hello: This patch was applied to netdev/net-next.git (refs/heads/master): On Thu, 1 Apr 2021 17:57:05 +0200 you wrote: > If there is overlapp between ip_local_port_range and ip_local_reserved_ports with a huge reserved block, it will affect probability of selecting ephemeral ports, see file net/ipv4/inet_hashtables.c:723 > > int __inet_hash_connect( > ... > for (i = 0; i < remaining; i += 2, port += 2) { > if (unlikely(port >= high)) > port -= remaining; > if (inet_is_local_reserved_port(net, port)) > continue; > > [...] Here is the summary with links: - [net-next] net: document a side effect of ip_local_reserved_ports https://git.kernel.org/netdev/net-next/c/a7a80b17c750 You are awesome, thank you! -- Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index c7952ac5bd2f..74c458d2686a 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -1073,7 +1073,9 @@ ip_local_reserved_ports - list of comma separated ranges although this is redundant. However such a setting is useful if later the port range is changed to a value that will - include the reserved ports. + include the reserved ports. Also keep in mind, that overlapping + of these ranges may affect probability of selecting ephemeral + ports which are right after block of reserved ports. Default: Empty
If there is overlapp between ip_local_port_range and ip_local_reserved_ports with a huge reserved block, it will affect probability of selecting ephemeral ports, see file net/ipv4/inet_hashtables.c:723 int __inet_hash_connect( ... for (i = 0; i < remaining; i += 2, port += 2) { if (unlikely(port >= high)) port -= remaining; if (inet_is_local_reserved_port(net, port)) continue; E.g. if there is reserved block of 10000 ports, two ports right after this block will be 5000 more likely selected than others. If this was intended, we can/should add note into documentation as proposed in this commit, otherwise we should think about different solution. One option could be mapping table of continuous port ranges. Second option could be letting user to modify step (port+=2) in above loop, e.g. using new sysctl parameter. Signed-off-by: Otto Hollmann <otto.hollmann@suse.com> --- Documentation/networking/ip-sysctl.rst | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)