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Hannu Varjoranta
f8932b2c0c
Since commit014c607f86("gve: add support for UDP GSO for DQO format"), gve_prep_tso() matches shinfo->gso_type exactly. gso_type is a bitmask, though: SKB_GSO_DODGY is set on every GSO packet that comes from tun/tap, packet sockets or other untrusted sources, and SKB_GSO_TCP_ECN and SKB_GSO_TCP_FIXEDID can be set as well. Such packets hit the default case, gve_tx_add_skb_dqo() fails and gve_try_tx_skb() drops them, counting them in tx_dropped. These packets do reach the driver: tcp_gso_segment() passes DODGY skbs through unsegmented to devices that support TSO, after recomputing gso_segs, so drivers must tolerate the bit. This breaks virtual machines behind a tap on GCE instances using the DQO queue formats. Every TSO packet forwarded from a guest (gso_type SKB_GSO_TCPV4 | SKB_GSO_DODGY) is dropped, and guest uploads slow to a crawl of retransmissions or stall entirely, while the host's own TSO traffic (gso_type SKB_GSO_TCPV4) is unaffected. On an n4 instance (DQO-QPL) with a Cloud Hypervisor guest, a 64 MB upload from the guest went from a 60 s timeout at ~0.9 MB/s to 0.19 s with this change, with tx_dropped no longer increasing. Host TCP with ECN is hit as well: gve advertises NETIF_F_TSO_ECN, so a TSO packet carrying CWR has SKB_GSO_TCP_ECN set and is dropped too. Restore the bitmask test that commit1b9f756344("gve: ignore nonrelevant GSO type bits when processing TSO headers") introduced for the same problem, keeping the UDP GSO support. While here, reload shinfo after skb_cow_head(). If the head was cloned, pskb_expand_head() moves skb_shared_info to the new head, and the pointer cached at function entry can then refer to memory that another clone frees. Fixes:014c607f86("gve: add support for UDP GSO for DQO format") Signed-off-by: Hannu Varjoranta <[email protected]> Reviewed-by: Eric Dumazet <[email protected]> Reviewed-by: Ankit Garg <[email protected]> Reviewed-by: Harshitha Ramamurthy <[email protected]> Link: https://patch.msgid.link/[email protected] Signed-off-by: Paolo Abeni <[email protected]>