lab: multi-line answer boxes, one sheet per student

The fill-in fields put the label on its own line with dotted lines to write
on. handout.tex takes \studentnum and \studenthex; build-class.py compiles
one copy per student with the prefix filled in, checks each is two pages
and joins them for double-sided printing.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

docs/lab/handout/build-class.py

@@ -0,0 +1,63 @@
+#!/usr/bin/env python3
+"""One exercise sheet per student, with their prefix filled in, in one PDF.
+
+    python3 build-class.py 100            # students 1..100 -> class.pdf
+    python3 build-class.py 100 -o out.pdf
+    python3 build-class.py 5 12 -o few.pdf   # students 5..12
+
+Student n gets 2a0d:d741:<n in hex>::/48; the lab /40 allows 1..255. Each
+sheet is compiled separately and must come out to exactly two pages, so
+the result prints double-sided with one student per leaf. Needs pdflatex
+and pdfunite (poppler).
+"""
+import argparse
+import os
+import shutil
+import subprocess
+import sys
+import tempfile
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+
+
+def page_count(pdf):
+    out = subprocess.run(["pdfinfo", pdf], capture_output=True, text=True, check=True).stdout
+    return int(next(line.split()[-1] for line in out.splitlines() if line.startswith("Pages:")))
+
+
+def main():
+    ap = argparse.ArgumentParser(description=__doc__.split("\n")[0])
+    ap.add_argument("first", type=int, help="first student number, or the count if it is the only number")
+    ap.add_argument("last", type=int, nargs="?")
+    ap.add_argument("-o", "--output", default=os.path.join(HERE, "class.pdf"))
+    args = ap.parse_args()
+    first, last = (1, args.first) if args.last is None else (args.first, args.last)
+    if not 1 <= first <= last <= 255:
+        sys.exit("student numbers must be within 1..255: the lab /40 has 255 usable /48s")
+
+    with tempfile.TemporaryDirectory() as tmp:
+        for name in os.listdir(HERE):
+            if name.endswith((".tex", ".cls", ".sty", ".bst", ".bib")):
+                shutil.copy(os.path.join(HERE, name), tmp)
+        parts = []
+        for n in range(first, last + 1):
+            job = f"student-{n:03d}"
+            tex = f"\\def\\studentnum{{{n}}}\\def\\studenthex{{{n:x}}}\\input{{handout.tex}}"
+            for _ in range(2):  # twice, for the figure and table references
+                r = subprocess.run(["pdflatex", "-interaction=nonstopmode", "-halt-on-error", "-jobname", job, tex],
+                                   cwd=tmp, capture_output=True, text=True)
+                if r.returncode != 0:
+                    sys.exit(f"student {n}: pdflatex failed:\n{r.stdout[-2000:]}")
+            pdf = os.path.join(tmp, job + ".pdf")
+            pages = page_count(pdf)
+            if pages != 2:
+                sys.exit(f"student {n}: sheet is {pages} pages, not 2; double-sided printing would misalign")
+            parts.append(pdf)
+            print(f"\rstudent {n}: 2a0d:d741:{n:x}::/48", end="", flush=True)
+        print()
+        subprocess.run(["pdfunite", *parts, args.output], check=True)
+    print(f"wrote {args.output}: students {first}..{last}, {page_count(args.output)} pages")
+
+
+if __name__ == "__main__":
+    main()

docs/lab/handout/handout.tex

@@ -23,7 +23,17 @@
 
 % ---- things to change per class -------------------------------------------
 \newcommand{\laburl}{https://bgplab.rayhaan.net/}
-\newcommand{\myprefix}{\texttt{2a0d:d741:}\underline{\texttt{\,n\,}}\texttt{::/48}}
+% build-class.py compiles one copy per student with \studentnum and
+% \studenthex defined (e.g. 26 and 1a); without them this is the blank sheet.
+\providecommand{\studentnum}{}
+\providecommand{\studenthex}{}
+\ifx\studentnum\empty
+  \newcommand{\myprefix}{\texttt{2a0d:d741:}\underline{\texttt{\,n\,}}\texttt{::/48}}
+  \newcommand{\nhex}{<n>}
+\else
+  \newcommand{\myprefix}{\texttt{2a0d:d741:\studenthex::/48}}
+  \newcommand{\nhex}{\studenthex}
+\fi
 
 % ---- exercise machinery ------------------------------------------------------
 \lstset{basicstyle=\ttfamily\small,columns=fullflexible,keepspaces=true,
@@ -54,6 +64,7 @@
 \maketitle
 
 \medskip\noindent
+\ifx\studentnum\empty
 \parbox[t]{0.44\linewidth}{Name:~\dotfill}\hfill
 \parbox[t]{0.27\linewidth}{Prefix: \myprefix}
 
@@ -62,6 +73,14 @@ Your prefix is \myprefix, where \texttt{n} is your number \emph{in
 hexadecimal}.\par\noindent
 Student 10 has \texttt{2a0d:d741:a::/48} and student 26 has
 \texttt{2a0d:d741:1a::/48}.
+\else
+\parbox[t]{0.44\linewidth}{Name:~\dotfill}\hfill
+\parbox[t]{0.5\linewidth}{Student \studentnum\quad Prefix: \myprefix}
+
+\smallskip\noindent
+Your prefix is \myprefix: student number \studentnum, written in
+hexadecimal. Make sure to use this prefix in the exercise.
+\fi
 
 % ==============================================================================
 \section{Who Announces the Address You Are Using?}
@@ -76,8 +95,8 @@ announces that prefix.
 The RIPE database  records who holds address space
 (\texttt{inet6num}, or \texttt{inetnum} for IPv4) and who may announce it
 (\texttt{route6}, \texttt{route}). Look up your IPv6 address, then your lab prefix:
-\begin{lstlisting}
+\begin{lstlisting}[escapeinside={(*}{*)}]
-whois <your IPv6 address>        whois 2a0d:d741:<n>::/48
+whois <your IPv6 address>        whois 2a0d:d741:(*\nhex*)::/48
 \end{lstlisting}
 \fillintwo{Your IPv6 address: held by (\texttt{netname})}{\texttt{origin} AS:}
 \fillintwo{Your lab prefix: \texttt{origin} AS}{is it announced right now?}
@@ -116,7 +135,7 @@ Click \emph{bytes} next to your route and hover over the coloured segments.
 \fillintwo{AS number(s) in \texttt{AS\_PATH}:}{attribute carrying your prefix:}
 
 \task{See it from outside.}
-Wait a moment, then look your prefix up on \texttt{bgp.tools}.
+Wait a moment, then look your prefix up on \texttt{https://bgp.tools/super-lg}.
 \fillintwo{Origin AS the world sees:}{an AS path you found:}
 \noindent The lab daemon's AS4200000001 is missing from that path. Where did it go, and why?
 \answer[2]
@@ -124,7 +143,7 @@ Wait a moment, then look your prefix up on \texttt{bgp.tools}.
 \task{Reach it.}
 The router answers for every address in the lab space, so your prefix is
 reachable exactly when your announcement got out:\quad
-\texttt{ping -6 2a0d:d741:<n>::1}
+\texttt{ping -6 2a0d:d741:\nhex::1}
 \reach
 
 % ==============================================================================
@@ -154,7 +173,7 @@ Announce your prefix again with \texttt{210036:0:0} and
 \texttt{210036:1:42476}; announcing a prefix you own replaces it. Before you
 look: who do you expect to still see it?
 \answer[2]
-\noindent Wait a moment, then check on \texttt{bgp.tools} and with \texttt{ping}.
+\noindent Wait a moment, then check on \texttt{https://bgp.tools/super-lg} and with \texttt{ping}.
 \reach
 
 \task{To SWITCH only.}
@@ -162,7 +181,7 @@ Add \texttt{42476:0:0} and \texttt{42476:1:559} to the two you already have and
 announce again. Our router now tells only the route servers, and they tell
 only SWITCH.
 \reach
-\noindent Is your prefix still visible on \texttt{bgp.tools}? Explain what you see.
+\noindent Is your prefix still visible on \texttt{https://bgp.tools/super-lg}? Explain what you see.
 \answer[2]
 
 \task{Use of large communities.}