Test:
I observed that the "hdr_len" is 116 for this packet:
17:36:18.241105 52:55:00:d1:27:0a > 2e:2c:df:46:a9:e1, ethertype IPv4
(0x0800), length 2912: (tos 0x0, ttl 64, id 45197, offset 0, flags [none],
proto UDP (17), length 2898)
192.168.122.100.50613 > 192.168.122.1.4789: [bad udp cksum 0x8106
-> 0x26a0!] VXLAN, flags [I] (0x08), vni 1
fa:c3:ba:82:05:ee > ce:85:0c:31:77:e5, ethertype IPv4 (0x0800), length
2862: (tos 0x0, ttl 64, id 14678, offset 0, flags [DF], proto TCP (6), length
2848)
192.168.3.1.49880 > 192.168.3.2.9898: Flags [P.], cksum 0x9266
(incorrect -> 0xaa20), seq 515667:518463, ack 1, win 64, options [nop,nop,TS
val 2990048824 ecr 2798801412], length 2796
116 = 14(mac) + 20(ip) + 8(udp) + 8(vxlan) + 14(inner mac) + 20(inner ip) +
32(innner tcp)
