From e9f92c88163841d3f1d29fa5b44ae4c6f71bb014 Mon Sep 17 00:00:00 2001

From: Daan De Meyer <daan.j.demeyer@gmail.com>

Date: Wed, 18 Aug 2021 07:59:13 +0100

Subject: [PATCH] udev: Support "max" string for BufferSize options (#20458)

"max" indicates the hardware advertised maximum queue buffer size

should be used.

The max sizes can be checked by running `ethtool -g <dev>` (Preset maximums).

Since the buffer sizes can't be set to 0 by users, internally we use 0 to

indicate that the hardware advertised maximum should be used.

---

 man/systemd.link.xml      | 20 ++++++++++++--------

 src/shared/ethtool-util.c | 40 +++++++++++++++++++++++++--------------

 src/shared/ethtool-util.h |  2 ++

 3 files changed, 40 insertions(+), 22 deletions(-)

diff --git a/man/systemd.link.xml b/man/systemd.link.xml

index 1c18f35fc8..fd744ebaed 100644

--- a/man/systemd.link.xml

+++ b/man/systemd.link.xml

@@ -735,29 +735,33 @@

       <varlistentry>

         <term><varname>RxBufferSize=</varname></term>

         <listitem>

-          <para>Takes an integer. Specifies the maximum number of pending packets in the NIC receive buffer.

-          When unset, the kernel's default will be used.</para>

+          <para>Takes an integer or <literal>max</literal>. Specifies the maximum number of pending packets

+          in the NIC receive buffer. When unset, the kernel's default will be used. If set to

+          <literal>max</literal>, the hardware's advertised maximum size will be used.</para>

         </listitem>

       </varlistentry>

       <varlistentry>

         <term><varname>RxMiniBufferSize=</varname></term>

         <listitem>

-          <para>Takes an integer. Specifies the maximum number of pending packets in the NIC mini receive buffer.

-          When unset, the kernel's default will be used.</para>

+          <para>Takes an integer or <literal>max</literal>. Specifies the maximum number of pending packets

+          in the NIC mini receive buffer. When unset, the kernel's default will be used. If set to

+          <literal>max</literal>, the hardware's advertised maximum size will be used.</para>

         </listitem>

       </varlistentry>

       <varlistentry>

         <term><varname>RxJumboBufferSize=</varname></term>

         <listitem>

-          <para>Takes an integer. Specifies the maximum number of pending packets in the NIC jumbo receive buffer.

-          When unset, the kernel's default will be used.</para>

+          <para>Takes an integer or <literal>max</literal>. Specifies the maximum number of pending packets

+          in the NIC jumbo receive buffer. When unset, the kernel's default will be used. If set to

+          <literal>max</literal>, the hardware's advertised maximum size will be used.</para>

         </listitem>

       </varlistentry>

       <varlistentry>

         <term><varname>TxBufferSize=</varname></term>

         <listitem>

-          <para>Takes an integer. Specifies the maximum number of pending packets in the NIC transmit buffer.

-          When unset, the kernel's default will be used.</para>

+          <para>Takes an integer or <literal>max</literal>. Specifies the maximum number of pending packets

+          in the NIC transmit buffer. When unset, the kernel's default will be used. If set to

+          <literal>max</literal>, the hardware's advertised maximum size will be used.</para>

         </listitem>

       </varlistentry>

       <varlistentry>

diff --git a/src/shared/ethtool-util.c b/src/shared/ethtool-util.c

index f77f6943ca..ed251ec8dd 100644

--- a/src/shared/ethtool-util.c

+++ b/src/shared/ethtool-util.c

@@ -399,16 +399,24 @@ int ethtool_set_nic_buffer_size(int *ethtool_fd, const char *ifname, const netde

                 return -errno;

         if (ring->rx_pending_set)

-                UPDATE(ecmd.rx_pending, ring->rx_pending, need_update);

+                UPDATE(ecmd.rx_pending,

+                       ring->rx_pending == 0 ? ecmd.rx_max_pending : ring->rx_pending,

+                       need_update);

         if (ring->rx_mini_pending_set)

-                UPDATE(ecmd.rx_mini_pending, ring->rx_mini_pending, need_update);

+                UPDATE(ecmd.rx_mini_pending,

+                       ring->rx_mini_pending == 0 ? ecmd.rx_mini_max_pending : ring->rx_mini_pending,

+                       need_update);

         if (ring->rx_jumbo_pending_set)

-                UPDATE(ecmd.rx_jumbo_pending, ring->rx_jumbo_pending, need_update);

+                UPDATE(ecmd.rx_jumbo_pending,

+                       ring->rx_jumbo_pending == 0 ? ecmd.rx_jumbo_max_pending : ring->rx_jumbo_pending,

+                       need_update);

         if (ring->tx_pending_set)

-                UPDATE(ecmd.tx_pending, ring->tx_pending, need_update);

+                UPDATE(ecmd.tx_pending,

+                       ring->tx_pending == 0 ? ecmd.tx_max_pending : ring->tx_pending,

+                       need_update);

         if (!need_update)

                 return 0;

@@ -1037,16 +1045,20 @@ int config_parse_nic_buffer_size(

         assert(rvalue);

         assert(data);

-        r = safe_atou32(rvalue, &k);

-        if (r < 0) {

-                log_syntax(unit, LOG_WARNING, filename, line, r,

-                           "Failed to parse interface buffer value, ignoring: %s", rvalue);

-                return 0;

-        }

-        if (k < 1) {

-                log_syntax(unit, LOG_WARNING, filename, line, 0,

-                           "Invalid %s= value, ignoring: %s", lvalue, rvalue);

-                return 0;

+        if (streq(rvalue, "max"))

+                k = 0;

+        else {

+                r = safe_atou32(rvalue, &k);

+                if (r < 0) {

+                        log_syntax(unit, LOG_WARNING, filename, line, r,

+                                "Failed to parse interface buffer value, ignoring: %s", rvalue);

+                        return 0;

+                }

+                if (k < 1) {

+                        log_syntax(unit, LOG_WARNING, filename, line, 0,

+                                "Invalid %s= value, ignoring: %s", lvalue, rvalue);

+                        return 0;

+                }

         }

         if (streq(lvalue, "RxBufferSize")) {

diff --git a/src/shared/ethtool-util.h b/src/shared/ethtool-util.h

index 7d28766624..aea131914e 100644

--- a/src/shared/ethtool-util.h

+++ b/src/shared/ethtool-util.h

@@ -70,6 +70,8 @@ typedef struct netdev_channels {

 } netdev_channels;

 typedef struct netdev_ring_param {

+        /* For any of the 4 following settings, a value of 0 indicates the hardware advertised maximum should

+         * be used. */

         uint32_t rx_pending;

         uint32_t rx_mini_pending;

         uint32_t rx_jumbo_pending;

-- 

2.31.1