From 40e31579de9796ed91883d1f388ed2f565c2d69b Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Thu, 22 May 2025 01:33:55 +0200 Subject: [PATCH] conn: don't enable GRO on Linux < 5.12 Kernels below 5.12 are missing this: commit 98184612aca0a9ee42b8eb0262a49900ee9eef0d Author: Norman Maurer Date: Thu Apr 1 08:59:17 2021 net: udp: Add support for getsockopt(..., ..., UDP_GRO, ..., ...); Support for UDP_GRO was added in the past but the implementation for getsockopt was missed which did lead to an error when we tried to retrieve the setting for UDP_GRO. This patch adds the missing switch case for UDP_GRO Fixes: e20cf8d3f1f7 ("udp: implement GRO for plain UDP sockets.") Signed-off-by: Norman Maurer Reviewed-by: David Ahern Signed-off-by: David S. Miller That means we can't set the option and then read it back later. Given how buggy UDP_GRO is in general on odd kernels, just disable it on older kernels all together. Signed-off-by: Jason A. Donenfeld --- conn/controlfns_linux.go | 48 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) diff --git a/conn/controlfns_linux.go b/conn/controlfns_linux.go index 7bd3917..f0deefa 100644 --- a/conn/controlfns_linux.go +++ b/conn/controlfns_linux.go @@ -13,6 +13,35 @@ import ( "golang.org/x/sys/unix" ) +// Taken from go/src/internal/syscall/unix/kernel_version_linux.go +func kernelVersion() (major, minor int) { + var uname unix.Utsname + if err := unix.Uname(&uname); err != nil { + return + } + + var ( + values [2]int + value, vi int + ) + for _, c := range uname.Release { + if '0' <= c && c <= '9' { + value = (value * 10) + int(c-'0') + } else { + // Note that we're assuming N.N.N here. + // If we see anything else, we are likely to mis-parse it. + values[vi] = value + vi++ + if vi >= len(values) { + break + } + value = 0 + } + } + + return values[0], values[1] +} + func init() { controlFns = append(controlFns, @@ -57,5 +86,24 @@ func init() { } return err }, + + // Attempt to enable UDP_GRO + func(network, address string, c syscall.RawConn) error { + // Kernels below 5.12 are missing 98184612aca0 ("net: + // udp: Add support for getsockopt(..., ..., UDP_GRO, + // ..., ...);"), which means we can't read this back + // later. We could pipe the return value through to + // the rest of the code, but UDP_GRO is kind of buggy + // anyway, so just gate this here. + major, minor := kernelVersion() + if major < 5 || (major == 5 && minor < 12) { + return nil + } + + c.Control(func(fd uintptr) { + _ = unix.SetsockoptInt(int(fd), unix.IPPROTO_UDP, unix.UDP_GRO, 1) + }) + return nil + }, ) }