symbol conflicts between netinet/in.h, arpa/inet.h, and rte_ip.h

[Matthew Hall <mhall-Hv3ogNYU3JfZZajBQzqCxQ@public.gmane.org>]

Hello,

I ran into some weird symbol conflicts between system netinet/in.h and DPDK 
rte_ip.h. They have a lot of duplicated definitions for stuff like IPPROTO_IP 
and so on. This breaks when you want to use inet_pton from arpa/inet.h, 
because it includes netinet/in.h to define struct in_addr.

Thus with all the conflicts it's impossible to use a DPDK IP struct instead of 
all the system's sockaddr stuff, to store a value from the system copy of 
inet_pton. This would be a common operation if, for example, you want to 
configure all the IP addresses on your box from a JSON file, which is what I 
was doing.

The DPDK kludged around it internally by using a file called 
cmdline_parse_ipaddr.c with private copies of these functions. But it in my 
opinion very unwisely marked all of the functions as static except for 
cmdline_parse_ipaddr, which only works on the DPDK's proprietary argument 
handling, and not with anything the user might have which is a different 
format.

So, it would be a big help for users if the macros in librte_net files would 
check if the symbols already existed, or if they had subheader files available 
to grab only non conflicting symbols, or if they would make a proper .h and 
factor all the inet_pton and inet_ntop inside the cmdline lib into a place 
where users can access them. It would also be a help if they had a less ugly 
equivalent to struct sockaddr, which let you work with IP addresses a bit more 
easily, such as something like this:

struct ip4_addr {
    uint32_t addr;
};

typedef struct ip4_addr ip4_addr;

struct ip6_addr {
    uint8_t addr[16];
};

typedef struct ip6_addr ip6_addr;

struct ip_addr {
    uint8_t family;
    uint8_t prefix;
    union {
        struct ip4_addr ipv4;
        struct ip6_addr ipv6;
    };
};

I had to create a bunch of duplicate code to handle it in my project, since 
the DPDK marked its copies of all these functions as "secret" and didn't make 
a .h for them. If any of it is useful I am happy to donate it, although I 
don't think I've got quite enough experience with this specifc part of the 
DPDK to code it up all by myself.

Thanks,
Matthew.