quic: fix build failure on older Linux versions

[maxmouchet]

The netinet/udp.h header is included twice in QUIC probe modules: once directly, and once through lib/includes.h.

This causes a build issue on older Linux versions (3.10):

/root/zmapv6/src/probe_modules/module_quic_initial.c: In function _quic_initial_make_packet_:                                                                    
/root/zmapv6/src/probe_modules/module_quic_initial.c:145:12: error: _struct udphdr_ has no member named _uh_sport_                                               
  udp_header->uh_sport =                                                                                                                                         
            ^                                                                                                                                                    
/root/zmapv6/src/probe_modules/module_quic_initial.c:176:12: error: _struct udphdr_ has no member named _uh_ulen_                                                
  udp_header->uh_ulen = ntohs(sizeof(struct udphdr) + payload_len);                                                                                              
            ^                                                                                                                                                    
In file included from /usr/include/bits/byteswap.h:35:0,                                                                                                         
                 from /usr/include/endian.h:60,                                                                                                                  
                 from /usr/include/sys/types.h:216,                                                                                                              
                 from /usr/include/netinet/udp.h:51,                                                                                                             
                 from /root/zmapv6/src/probe_modules/module_quic_initial.c:13:                                                                                   
/root/zmapv6/src/probe_modules/module_quic_initial.c: In function _quic_initial_print_packet_:                                                                   
/root/zmapv6/src/probe_modules/module_quic_initial.c:193:13: error: _struct udphdr_ has no member named _uh_sport_                                               
   ntohs(udph->uh_sport), ntohs(udph->uh_dport),                            

I think this is because in older kernels the udphdr struct was defined through an ifdef:

/* UDP header as specified by RFC 768, August 1980. */
#ifdef __FAVOR_BSD

struct udphdr
{
  u_int16_t uh_sport;                /* source port */
  u_int16_t uh_dport;                /* destination port */
  u_int16_t uh_ulen;                /* udp length */
  u_int16_t uh_sum;                /* udp checksum */
};

#else

struct udphdr
{
  u_int16_t source;
  u_int16_t dest;
  u_int16_t len;
  u_int16_t check;
};
#endif

Whereas it's a union in newer kernels.

Including the header through lib/includes.h fixes the issue because it defines __FAVOR_BSD if not already defined.

[ogasser]

These changes look good to me 👍

The main issue is that in these files we were including netinet/udp.h before includes.h. output_modules/module_json.c also includes netinet/udp.h, but does not run into this issue due to includes.h being included first.

So from my side this looks good to be merged. What do you think @zirngibl @sattler ?

[zirngibl]

Sorry for the late reply but looks good to me as well