udev: support to update flow control parameter

Closes #14770.

man/systemd.link.xml

@@ -700,6 +700,30 @@
           <para>Takes a integer. Specifies the NIC transmit ring buffer size. When unset, the kernel's default will be used.</para>
         </listitem>
       </varlistentry>
+      <varlistentry>
+        <term><varname>RxFlowControl=</varname></term>
+        <listitem>
+          <para>Takes a boolean. When set, enables the receive flow control, also known as the ethernet
+          receive PAUSE message (generate and send ethernet PAUSE frames). When unset, the kernel's
+          default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>TxFlowControl=</varname></term>
+        <listitem>
+          <para>Takes a boolean. When set, enables the transmit flow control, also known as the ethernet
+          transmit PAUSE message (respond to received ethernet PAUSE frames). When unset, the kernel's
+          default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>AutoNegotiationFlowControl=</varname></term>
+        <listitem>
+          <para>Takes a boolean. When set, the auto negotiation enables the interface to exchange state
+          advertisements with the connected peer so that the two devices can agree on the ethernet
+          PAUSE configuration. When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
 
     </variablelist>
   </refsect1>

src/shared/ethtool-util.c

@@ -851,6 +851,55 @@ int ethtool_set_channels(int *fd, const char *ifname, netdev_channels *channels)
         return 0;
 }
 
+int ethtool_set_flow_control(int *fd, const char *ifname, int rx, int tx, int autoneg) {
+        struct ethtool_pauseparam ecmd = {
+                .cmd = ETHTOOL_GPAUSEPARAM
+        };
+        struct ifreq ifr = {
+                .ifr_data = (void*) &ecmd
+        };
+
+        bool need_update = false;
+        int r;
+
+        if (*fd < 0) {
+                r = ethtool_connect_or_warn(fd, true);
+                if (r < 0)
+                        return r;
+        }
+
+        strscpy(ifr.ifr_name, IFNAMSIZ, ifname);
+
+        r = ioctl(*fd, SIOCETHTOOL, &ifr);
+        if (r < 0)
+                return -errno;
+
+        if (rx >= 0 && ecmd.rx_pause != (uint32_t) rx) {
+                ecmd.rx_pause = rx;
+                need_update = true;
+        }
+
+        if (tx >= 0 && ecmd.tx_pause != (uint32_t) tx) {
+                ecmd.tx_pause = tx;
+                need_update = true;
+        }
+
+        if (autoneg >= 0 && ecmd.autoneg != (uint32_t) autoneg) {
+                ecmd.autoneg = autoneg;
+                need_update = true;
+        }
+
+        if (need_update) {
+                ecmd.cmd = ETHTOOL_SPAUSEPARAM;
+
+                r = ioctl(*fd, SIOCETHTOOL, &ifr);
+                if (r < 0)
+                        return -errno;
+        }
+
+        return 0;
+}
+
 int config_parse_channel(const char *unit,
                          const char *filename,
                          unsigned line,

src/shared/ethtool-util.h

@@ -103,6 +103,7 @@ int ethtool_set_glinksettings(int *ethtool_fd, const char *ifname,
                               int autonegotiation, uint32_t advertise[static N_ADVERTISE],
                               uint64_t speed, Duplex duplex, NetDevPort port);
 int ethtool_set_channels(int *ethtool_fd, const char *ifname, netdev_channels *channels);
+int ethtool_set_flow_control(int *fd, const char *ifname, int rx, int tx, int autoneg);
 
 const char *duplex_to_string(Duplex d) _const_;
 Duplex duplex_from_string(const char *d) _pure_;

src/udev/net/link-config-gperf.gperf

@@ -60,3 +60,6 @@ Link.CombinedChannels,           config_parse_channel,                  0,
 Link.Advertise,                  config_parse_advertise,                0,                             offsetof(link_config, advertise)
 Link.RxBufferSize,               config_parse_nic_buffer_size,          0,                             offsetof(link_config, ring)
 Link.TxBufferSize,               config_parse_nic_buffer_size,          0,                             offsetof(link_config, ring)
+Link.RxFlowControl,              config_parse_tristate,                 0,                             offsetof(link_config, rx_flow_control)
+Link.TxFlowControl,              config_parse_tristate,                 0,                             offsetof(link_config, tx_flow_control)
+Link.AutoNegotiationFlowControl, config_parse_tristate,                 0,                             offsetof(link_config, autoneg_flow_control)

src/udev/net/link-config.c

@@ -148,6 +148,9 @@ int link_load_one(link_config_ctx *ctx, const char *filename) {
                 .duplex = _DUP_INVALID,
                 .port = _NET_DEV_PORT_INVALID,
                 .autonegotiation = -1,
+                .rx_flow_control = -1,
+                .tx_flow_control = -1,
+                .autoneg_flow_control = -1,
         };
 
         for (i = 0; i < ELEMENTSOF(link->features); i++)
@@ -409,6 +412,10 @@ int link_config_apply(link_config_ctx *ctx, link_config *config,
                         log_warning_errno(r, "Could not set ring buffer of %s: %m", old_name);
         }
 
+        r = ethtool_set_flow_control(&ctx->ethtool_fd, old_name, config->rx_flow_control, config->tx_flow_control, config->autoneg_flow_control);
+        if (r < 0)
+                log_warning_errno(r, "Could not set flow control of %s: %m", old_name);
+
         r = sd_device_get_ifindex(device, &ifindex);
         if (r < 0)
                 return log_device_warning_errno(device, r, "Could not find ifindex: %m");

src/udev/net/link-config.h

@@ -62,6 +62,9 @@ struct link_config {
         int features[_NET_DEV_FEAT_MAX];
         netdev_channels channels;
         netdev_ring_param ring;
+        int rx_flow_control;
+        int tx_flow_control;
+        int autoneg_flow_control;
 
         LIST_FIELDS(link_config, links);
 };

test/fuzz/fuzz-link-parser/directives.link

@@ -41,3 +41,6 @@ CombinedChannels=
 Advertise=
 RxBufferSize=
 TxBufferSize=
+RxFlowControl=
+TxFlowControl=
+AutoNegotiationFlowControl=