diff options
Diffstat (limited to 'pkg/tcpip/header')
| -rw-r--r-- | pkg/tcpip/header/ipv4.go | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/pkg/tcpip/header/ipv4.go b/pkg/tcpip/header/ipv4.go index 713d476d6..91fe7b6a5 100644 --- a/pkg/tcpip/header/ipv4.go +++ b/pkg/tcpip/header/ipv4.go @@ -89,7 +89,17 @@ type IPv4Fields struct { // DstAddr is the "destination ip address" of an IPv4 packet. DstAddr tcpip.Address - // Options is between 0 and 40 bytes or nil if empty. + // Options must be 40 bytes or less as they must fit along with the + // rest of the IPv4 header into the maximum size describable in the + // IHL field. RFC 791 section 3.1 says: + // IHL: 4 bits + // + // Internet Header Length is the length of the internet header in 32 + // bit words, and thus points to the beginning of the data. Note that + // the minimum value for a correct header is 5. + // + // That leaves ten 32 bit (4 byte) fields for options. An attempt to encode + // more will fail. Options IPv4Options } @@ -284,13 +294,10 @@ func (o IPv4Options) SizeWithPadding() int { return (len(o) + IPv4IHLStride - 1) & ^(IPv4IHLStride - 1) } -// Options returns a buffer holding the options or nil. +// Options returns a buffer holding the options. func (b IPv4) Options() IPv4Options { hdrLen := b.HeaderLength() - if hdrLen > IPv4MinimumSize { - return IPv4Options(b[options:hdrLen:hdrLen]) - } - return nil + return IPv4Options(b[options:hdrLen:hdrLen]) } // TransportProtocol implements Network.TransportProtocol. |