Fix Correct header detection in LegacyPcapReader

Replace `header_sent` flag with `consumed`. This fixes the pcap-info example to read asset/ntp.pcap file.

Author: zzzdong

src/pcap/reader.rs

@@ -72,7 +72,6 @@ where
  reader: R,
  buffer: Buffer,
  consumed: usize,
- header_sent: bool,
  reader_exhausted: bool,
  parse: LegacyParseFn,
 }
@@ -119,7 +118,6 @@ where
  reader,
  buffer,
  consumed: 0,
- header_sent: false,
  reader_exhausted: false,
  parse,
  })
@@ -131,8 +129,7 @@ where
  R: Read,
 {
  fn next(&mut self) -> Result<(usize, PcapBlockOwned), PcapError<&'_ [u8]>> {
- if !self.header_sent {
- self.header_sent = true;
+ if self.consumed == 0 {
  return Ok((
  self.header.size(),
  PcapBlockOwned::from(self.header.clone()),