Hi Ricky, ipip in the linux semantics refers usually to IP tunnel, for example: http://lxr.free-electrons.com/source/net/ipv4/ipip.c Traffic of ip tunnels is composed from an inner IP header which is encapsulated within a packet which as the external IP header, >(1) what is differences between ip_hdr and ipip_hdr? Why we have them? No ?>documentation whatever to figure it out. ip_hdr() is the IP header of layer 3, the network ipip_hdr() is the IP header of layer 4, the transport layer. So this is the IP header of the internal IP header when you have a tunnel, not the external IP header. Hope this helps, Regards, Rami Rosen http://ramirose.wix.com/ramirosen On 18 August 2016 at 11:47, Ricky <zhangchaowang@xxxxxxxxx> wrote: > > In include/linux/ip.h, > > 23 static inline struct iphdr *ip_hdr(const struct sk_buff *skb) > 24 { > 25 return (struct iphdr *)skb_network_header(skb); > 26 } > 27 > 28 static inline struct iphdr *inner_ip_hdr(const struct sk_buff *skb) > 29 { > 30 return (struct iphdr *)skb_inner_network_header(skb); > 31 } > 32 > 33 static inline struct iphdr *ipip_hdr(const struct sk_buff *skb) > 34 { > 35 return (struct iphdr *)skb_transport_header(skb); > 36 } > 37 #endif /* _LINUX_IP_H */ > > if I passed in sk_buff to ip_hdr and ipip_hdr > > struct iphdr *ip_hdr ip_hdr_net = ip_hdr(skb); > struct iphdr *ip_hdr ip_hdr_trans = ipip_hdr(skb); > > Do ip_hdr_net->saddr and ip_hdr_trans->saddr point to the same thing? I > tried it on code. It doesn't. It seems that only ip_hdr_net->saddr point to > source IP address, which make sense. Because network layer has IP but not on > transport layer. > > So questions: > > (1) what is differences between ip_hdr and ipip_hdr? Why we have them? No > documentation whatever to figure it out. > > (2) should I use ntohX function to convert ip_hdr member data when accessing > them? eg, ip_hdr_net->saddr. > > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@xxxxxxxxxxxxxxxxx > https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
