Merge pull request iovisor#407 from yadutaf/jt-readme

Documentation and tcp4connect enhancements

.gitignore

@@ -1,3 +1,7 @@
+# Editor's files
 *.swp
 *.swo
 *.pyc
+
+# Build artefacts
+/build/

INSTALL.md

@@ -112,12 +112,15 @@ To build the toolchain from source, one needs:
 
 ### Install build dependencies
 ```
+# Trusty and older
 VER=trusty
 echo "deb http:https://llvm.org/apt/$VER/ llvm-toolchain-$VER-3.7 main
 deb-src http:https://llvm.org/apt/$VER/ llvm-toolchain-$VER-3.7 main" | \
  sudo tee /etc/apt/sources.list.d/llvm.list
 wget -O - http:https://llvm.org/apt/llvm-snapshot.gpg.key | sudo apt-key add -
 sudo apt-get update
+
+# All versions
 sudo apt-get -y install bison build-essential cmake flex git libedit-dev \
  libllvm3.7 llvm-3.7-dev libclang-3.7-dev python zlib1g-dev
 ```

README.md

@@ -47,6 +47,10 @@ many possible capabilities.
 
 See [INSTALL.md](INSTALL.md) for installation steps on your platform.
 
+## FAQ
+
+See [FAQ.txt](FAQ.txt) for the most common troubleshoot questions.
+
 ## Contents
 
 Some of these are single files that contain both C and Python, others have a

examples/tracing/tcpv4connect.py

@@ -62,7 +62,7 @@
  bpf_probe_read(&dport, sizeof(dport), &skp->__sk_common.skc_dport);
 
  // output
- bpf_trace_printk("%x %x %d\\n", saddr, daddr, ntohs(dport));
+ bpf_trace_printk("trace_tcp4connect %x %x %d\\n", saddr, daddr, ntohs(dport));
 
  currsock.delete(&pid);
 
@@ -86,10 +86,19 @@ def inet_ntoa(addr):
  addr = addr >> 8
  return dq
 
-# format output
+# filter and format output
 while 1:
- (task, pid, cpu, flags, ts, msg) = b.trace_fields()
- (saddr_hs, daddr_hs, dport_s) = msg.split(" ")
+ # Read messages from kernel pipe
+ try:
+ (task, pid, cpu, flags, ts, msg) = b.trace_fields()
+ (_tag, saddr_hs, daddr_hs, dport_s) = msg.split(" ")
+ except ValueError:
+ # Ignore messages from other tracers
+ continue
+
+ # Ignore messages from other tracers
+ if _tag != "trace_tcp4connect":
+ continue
 
  print("%-6d %-12.12s %-16s %-16s %-4s" % (pid, task,
  inet_ntoa(int(saddr_hs, 16)),