sunvnet: generate ICMP PTMUD messages for smaller port MTUs

PATCH Superseded David L Stevens 1 participant 1 message Sep 12, 2014

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David L Stevens

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2014-09-12 23:19 UTC #0 lore raw

PATCH v2 3/3 sunvnet: generate ICMP PTMUD messages for smaller port MTUs

This patch sends ICMP and ICMPv6 messages for Path MTU Discovery when a remote port MTU is smaller than the device MTU. This allows mixing newer VIO protocol devices that support MTU negotiation with older devices that do not on the same vswitch. It also allows Linux-Linux LDOMs to use 64K-1 data packets even though Solaris vswitch is limited to <16K MTU.

Signed-off-by David L Stevens <[email protected]>

---
 drivers/net/ethernet/sun/sunvnet.c |   34 ++++++++++++++++++++++++++++++++++
 1 files changed, 34 insertions(+), 0 deletions(-)

drivers/net/ethernet/sun/sunvnet.c +34 -0

index b557ec4..b2381f0 100644
@@ -17,6 +17,13 @@
 #include <linux/mutex.h>
 #include <linux/if_vlan.h>
 
+#if IS_ENABLED(CONFIG_IPV6)
+#include <linux/icmpv6.h>
+#endif
+
+#include <net/icmp.h>
+#include <net/route.h>
+
 #include <asm/vio.h>
 #include <asm/ldc.h>

@@ -752,6 +759,33 @@ static int vnet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		goto out_dropped;
 
 	if (skb->len > port->vio.rmtu) {
+		unsigned long localmtu = port->vio.rmtu - ETH_HLEN;
+
+		if (port->vio.ver.major == 1 && port->vio.ver.minor >= 3)
+			localmtu -= VLAN_HLEN;
+
+		if (skb->protocol == htons(ETH_P_IP)) {
+			struct flowi4 fl4;
+			struct rtable *rt = NULL;
+
+			memset(&fl4, 0, sizeof(fl4));
+			fl4.flowi4_oif = dev->ifindex;
+			fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);
+			fl4.daddr = ip_hdr(skb)->daddr;
+			fl4.saddr = ip_hdr(skb)->saddr;
+
+			rt = ip_route_output_key(dev_net(dev), &fl4);
+			if (!IS_ERR(rt)) {
+				skb_dst_set(skb, &rt->dst);
+				icmp_send(skb, ICMP_DEST_UNREACH,
+					  ICMP_FRAG_NEEDED,
+					  htonl(localmtu));
+			}
+		}
+#if IS_ENABLED(CONFIG_IPV6)
+		else if (skb->protocol == htons(ETH_P_IPV6))
+			icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, localmtu);
+#endif
 		goto out_dropped;
 	}

Signature · 1 line

1.7.1