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iperf3: backport GSO/GRO fix for small packets #29658

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Merged
BKPepe merged 1 commit into from
Jun 6, 2026
Merged

iperf3: backport GSO/GRO fix for small packets #29658

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2 changes: 1 addition & 1 deletion net/iperf3/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk

PKG_NAME:=iperf
PKG_VERSION:=3.21
PKG_RELEASE:=1
PKG_RELEASE:=2

PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
PKG_SOURCE_URL:=https://downloads.es.net/pub/iperf
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45 changes: 45 additions & 0 deletions net/iperf3/patches/0001-Limit-UDP-GSO-number-of-segments-in-a-message-to-the.patch
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Original file line number Diff line number Diff line change
@@ -0,0 +1,45 @@
From 212a2fe3ae2e600617a1fde7e6a1a0a1488a341f Mon Sep 17 00:00:00 2001
From: DavidBar-On <david.cdb004@gmail.com>
Date: Sat, 2 May 2026 12:12:39 +0300
Subject: [PATCH] Limit UDP GSO number of segments in a message to the allowed
value

---
src/iperf.h | 1 +
src/iperf_client_api.c | 8 ++++++--
2 files changed, 7 insertions(+), 2 deletions(-)

--- a/src/iperf.h
+++ b/src/iperf.h
@@ -494,6 +494,7 @@ extern int gerror; /* error value from g
/* In Reverse mode, maximum number of packets to wait for "accept" response - to handle out of order packets */
#define MAX_REVERSE_OUT_OF_ORDER_PACKETS 2

+#define GSO_MAX_DG_IN_BF (1 << 7UL) // 128 - the Linux Kernel limit hardcoded as `UDP_MAX_SEGMENTS (1 << 7UL)` in `udpgso.c`
#define GSO_BF_MAX_SIZE MAX_UDP_BLOCKSIZE
#define GRO_BF_MAX_SIZE MAX_UDP_BLOCKSIZE

--- a/src/iperf_client_api.c
+++ b/src/iperf_client_api.c
@@ -420,7 +420,7 @@ iperf_handle_message_client(struct iperf
int
iperf_connect(struct iperf_test *test)
{
- int opt;
+ int opt, n;
socklen_t len;

if (NULL == test)
@@ -526,7 +526,11 @@ iperf_connect(struct iperf_test *test)
test->settings->gso_dg_size = test->settings->blksize;
/* use the multiple of datagram size for the best efficiency. */
if (test->settings->gso_dg_size > 0) {
- test->settings->gso_bf_size = (test->settings->gso_bf_size / test->settings->gso_dg_size) * test->settings->gso_dg_size;
+ n = test->settings->gso_bf_size / test->settings->gso_dg_size;
+ if (n > GSO_MAX_DG_IN_BF) {
+ n = GSO_MAX_DG_IN_BF;
+ }
+ test->settings->gso_bf_size = n * test->settings->gso_dg_size;
} else {
/* If gso_dg_size is 0 (unlimited bandwidth), use default UDP datagram size */
test->settings->gso_dg_size = DEFAULT_UDP_BLKSIZE;
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