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Combine/simplify conditional branches, eliminating dead code. See #1834

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This commit is contained in:
dmiller
2019-12-22 21:50:55 +00:00
parent 61d77a2165
commit 5abe0aa8cc
1 changed files with 13 additions and 14 deletions
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27
libnetutil/netutil.cc
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@@ -2420,11 +2420,14 @@ const char *ippackethdrinfo(const u8 *packet, u32 len, int detail) {
Snprintf(protoinfo, sizeof(protoinfo), "TCP %s:?? > %s:?? ?? %s (incomplete)",
srchost, dsthost, ipinfo);
}
/* For all cases after this, datalen is necessarily >= 8 and frag_off is <= 8 */
/* CASE 2: where we are missing the first 8 bytes of the TCP header but we
* have, at least, the next 8 bytes so we can see the ACK number, the
* flags and window size. */
else if (frag_off == 8 && datalen >= 8) {
else if (frag_off > 0) {
/* Fragmentation is on 8-byte boundaries, so 8 is the only legal value here. */
assert(frag_off == 8);
tcp = (struct tcp_hdr *)((u8 *) tcp - frag_off); // ugly?
/* TCP Flags */
@@ -2463,8 +2466,7 @@ const char *ippackethdrinfo(const u8 *packet, u32 len, int detail) {
}
/* Create a string with TCP information relevant to the specified level of detail */
if (detail == LOW_DETAIL) {
Snprintf(protoinfo, sizeof(protoinfo), "TCP %s:?? > %s:?? %s %s %s %s",
if (detail == LOW_DETAIL) { Snprintf(protoinfo, sizeof(protoinfo), "TCP %s:?? > %s:?? %s %s %s %s",
srchost, dsthost, tflags, ipinfo, tcpinfo, tcpoptinfo);
} else if (detail == MEDIUM_DETAIL) {
Snprintf(protoinfo, sizeof(protoinfo), "TCP %s:?? > %s:?? %s ack=%lu win=%hu %s IP [%s]",
@@ -2489,25 +2491,21 @@ const char *ippackethdrinfo(const u8 *packet, u32 len, int detail) {
}
}
}
/* For all cases after this, frag_off is necessarily 0 */
/* CASE 3: where the IP packet is not a fragment but for some reason, we
* don't have the entire TCP header, just part of it.*/
else if (datalen > 0 && datalen < 20) {
/* We only have the first 32 bits: source and dst port */
if (datalen >= 4 && datalen < 8) {
Snprintf(protoinfo, sizeof(protoinfo), "TCP %s:%hu > %s:%hu ?? (incomplete) %s",
srchost, (unsigned short) ntohs(tcp->th_sport), dsthost, (unsigned short) ntohs(tcp->th_dport), ipinfo);
}
else if (datalen < 20) {
/* We know we have the first 8 bytes, so what's left? */
/* We only have the first 64 bits: ports and seq number */
if (datalen >= 8 && datalen < 12) {
if (datalen < 12) {
Snprintf(tcpinfo, sizeof(tcpinfo), "TCP %s:%hu > %s:%hu ?? seq=%lu (incomplete) %s",
srchost, (unsigned short) ntohs(tcp->th_sport), dsthost,
(unsigned short) ntohs(tcp->th_dport), (unsigned long) ntohl(tcp->th_seq), ipinfo);
}
/* We only have the first 96 bits: ports, seq and ack number */
if (datalen >= 12 && datalen < 16) {
else if (datalen < 16) {
if (detail == LOW_DETAIL) { /* We don't print ACK in low detail */
Snprintf(tcpinfo, sizeof(tcpinfo), "TCP %s:%hu > %s:%hu seq=%lu (incomplete), %s",
srchost, (unsigned short) ntohs(tcp->th_sport), dsthost,
@@ -2520,8 +2518,8 @@ const char *ippackethdrinfo(const u8 *packet, u32 len, int detail) {
}
}
/* We are missing the last 32 bits (checksum and urgent pointer) */
if (datalen >= 16 && datalen < 20) {
/* We are missing some part of the last 32 bits (checksum and urgent pointer) */
else {
p = tflags;
/* These are basically in tcpdump order */
if (tcp->th_flags & TH_SYN)
@@ -2638,6 +2636,7 @@ const char *ippackethdrinfo(const u8 *packet, u32 len, int detail) {
} else{
/* If the packet does not fall into any other category, then we have a
really screwed-up packet. */
/* This ought to be unreachable; if static analysis flags it as such, delete it. */
Snprintf(protoinfo, sizeof(protoinfo), "TCP %s:?? > %s:?? ?? %s (invalid TCP)",
srchost, dsthost, ipinfo);
}