encap_mtu 535 include/net/dst.h u32 encap_mtu = dst_mtu(encap_dst); encap_mtu 537 include/net/dst.h if (skb->len > encap_mtu - headroom) encap_mtu 538 include/net/dst.h skb_dst_update_pmtu_no_confirm(skb, encap_mtu - headroom);