Add support for HTTP 1.1 If-Modified-Since behavior.

fetch(1) accepts a new argument -i <file> that if specified will cause
the file to be downloaded only if it is more recent than the mtime of
<file>.

libfetch(3) accepts the mtime in the url structure and a flag to
indicate when this behavior is desired.

PR:		bin/87841
Submitted by:	Jukka A. Ukkonen <jau@iki.fi> (partially)
Reviewed by:	des, ru
MFC after:	3 weeks

1 files changed, 25 insertions, 4 deletions

diff --git a/usr.bin/fetch/fetch.c b/usr.bin/fetch/fetch.c
index e71e821..eda8048 100644
--- a/usr.bin/fetch/fetch.c
+++ b/usr.bin/fetch/fetch.c
@@ -60,6 +60,8 @@ int	 d_flag;	/*    -d: direct connection */
 int	 F_flag;	/*    -F: restart without checking mtime  */
 char	*f_filename;	/*    -f: file to fetch */
 char	*h_hostname;	/*    -h: host to fetch from */
+int	 i_flag;	/*    -i: specify input file for mtime comparison */
+char	*i_filename;	/*        name of input file */
 int	 l_flag;	/*    -l: link rather than copy file: URLs */
 int	 m_flag;	/* -[Mm]: mirror mode */
 char	*N_filename;	/*    -N: netrc file name */
@@ -382,6 +384,14 @@ fetch(char *URL, const char *path)
 		if (A_flag)
 			strcat(flags, "A");
 		timeout = T_secs ? T_secs : http_timeout;
+		if (i_flag) {
+			if (stat(i_filename, &sb)) {
+				warn("%s: stat()", i_filename);
+				goto failure;
+			}
+			url->ims_time = sb.st_mtime;
+			strcat(flags, "i");
+		}
 	}
 
 	/* set the protocol timeout. */
@@ -449,7 +459,14 @@ fetch(char *URL, const char *path)
 		goto signal;
 	if (f == NULL) {
 		warnx("%s: %s", URL, fetchLastErrString);
-		goto failure;
+		if (i_flag && strcmp(url->scheme, SCHEME_HTTP) == 0
+		    && fetchLastErrCode == FETCH_OK
+		    && strcmp(fetchLastErrString, "Not Modified") == 0) {
+			/* HTTP Not Modified Response, return OK. */
+			r = 0;
+			goto done;
+		} else
+			goto failure;
 	}
 	if (sigint)
 		goto signal;
@@ -713,9 +730,9 @@ usage(void)
 {
 	fprintf(stderr, "%s\n%s\n%s\n%s\n",
 "usage: fetch [-146AadFlMmnPpqRrsUv] [-B bytes] [-N file] [-o file] [-S bytes]",
-"       [-T seconds] [-w seconds] URL ...",
+"       [-T seconds] [-w seconds] [-i file] URL ...",
 "       fetch [-146AadFlMmnPpqRrsUv] [-B bytes] [-N file] [-o file] [-S bytes]",
-"       [-T seconds] [-w seconds] -h host -f file [-c dir]");
+"       [-T seconds] [-w seconds] [-i file] -h host -f file [-c dir]");
 }
 
 
@@ -732,7 +749,7 @@ main(int argc, char *argv[])
 	int c, e, r;
 
 	while ((c = getopt(argc, argv,
-	    "146AaB:bc:dFf:Hh:lMmN:nPpo:qRrS:sT:tUvw:")) != -1)
+	    "146AaB:bc:dFf:Hh:i:lMmN:nPpo:qRrS:sT:tUvw:")) != -1)
 		switch (c) {
 		case '1':
 			once_flag = 1;
@@ -777,6 +794,10 @@ main(int argc, char *argv[])
 		case 'h':
 			h_hostname = optarg;
 			break;
+		case 'i':
+			i_flag = 1;
+			i_filename = optarg;
+			break;
 		case 'l':
 			l_flag = 1;
 			break;