Fix bogus packet length calculation in the RX/LRO path, which can lead to

TSO tagging forwarded packets which shouldn't.  This will also fix the em(4)
watchdog timeouts seen after the em(4) TSO commit.

Thanks to Hrvoje Popovski for providing the infrastructure the reproduce
the issue, and test the fix.

Discussed with bluhm@.  OK claudio@

diff --git a/sys/dev/pci/if_ix.c b/sys/dev/pci/if_ix.c
index ddbfbe3..c623bb5 100644 (file)
--- a/sys/dev/pci/if_ix.c
+++ b/sys/dev/pci/if_ix.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: if_ix.c,v 1.208 2024/02/14 22:41:48 bluhm Exp $       */
+/*     $OpenBSD: if_ix.c,v 1.209 2024/02/15 10:56:53 mglocker Exp $    */
 
 /******************************************************************************
 
@@ -3260,20 +3260,24 @@ ixgbe_rxeof(struct rx_ring *rxr)
 
                        if (pkts > 1) {
                                struct ether_extracted ext;
-                               uint32_t hdrlen, paylen;
+                               uint32_t paylen;
 
-                               /* Calculate header size. */
+                               /*
+                                * Calculate the payload size:
+                                *
+                                * The packet length returned by the NIC
+                                * (sendmp->m_pkthdr.len) can contain
+                                * padding, which we don't want to count
+                                * in to the payload size.  Therefore, we
+                                * calculate the real payload size based
+                                * on the total ip length field (ext.iplen).
+                                */
                                ether_extract_headers(sendmp, &ext);
-                               hdrlen = sizeof(*ext.eh);
-#if NVLAN > 0
-                               if (ISSET(sendmp->m_flags, M_VLANTAG) ||
-                                   ext.evh)
-                                       hdrlen += ETHER_VLAN_ENCAP_LEN;
-#endif
+                               paylen = ext.iplen;
                                if (ext.ip4 || ext.ip6)
-                                       hdrlen += ext.iphlen;
+                                       paylen -= ext.iphlen;
                                if (ext.tcp) {
-                                       hdrlen += ext.tcphlen;
+                                       paylen -= ext.tcphlen;
                                        tcpstat_inc(tcps_inhwlro);
                                        tcpstat_add(tcps_inpktlro, pkts);
                                } else {
@@ -3285,8 +3289,6 @@ ixgbe_rxeof(struct rx_ring *rxr)
                                 * mark it as TSO, set a correct mss,
                                 * and recalculate the TCP checksum.
                                 */
-                               paylen = sendmp->m_pkthdr.len > hdrlen ?
-                                   sendmp->m_pkthdr.len - hdrlen : 0;
                                if (ext.tcp && paylen >= pkts) {
                                        SET(sendmp->m_pkthdr.csum_flags,
                                            M_TCP_TSO);