Improve input validation when when using IP_HDRINCL socket option on SOCK_RAW sockets

[tuexen]

Summary

When sending IPv4 packets on a SOCK_RAW socket using the IP_HDRINCL, ensure that the ip_hl field is valid. Furthermore, ensure that the complete IPv4 header is contained in the first mbuf. Finally, move the length checks before relying on them when accessing fields of the IPv4 header.

Thanks to jtl@ for bringing up these issues.

[jtl]

Thanks!

sys/netinet/raw_ip.c

530 ↗

(On Diff #53884)

I feel like this is a bit redundant. If m->m_pkthdr.len is set correctly, then the m_pullup should fail if m->m_pkthdr.len < hlen. (And, you've established on line 529 that ntohs(ip->ip_len) is equal to m->m_pkthdr.len.) However, to be clear, I do not strongly feel that this should be changed.

[tuexen]

Integrate jtl@'s suggestion.

[tuexen]

sys/netinet/raw_ip.c

530 ↗

(On Diff #53884)

I integrated your suggestion.